By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode(SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conductio...By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode(SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conduction characteristic is demonstrated by the verification of temperature-dependent current–voltage(I–V) tests and electroluminescence spectra.Meanwhile, apparently advantageous forward conduction properties as compared to the pn diode fabricated on the same wafer have been achieved, featuring a lower turn-on voltage of 0.82 V. Together with the analysis model established in the GaN SPND for a wide-range designable turn-on voltage, this work provides an alternative method to the GaN rectifier strategies besides the traditional solution.展开更多
Halide vapor phase epitaxy(HVPE) is widely used in the semiconductor industry for the growth of Si, GaAs, GaN, etc.HVPE is a non-organic chemical vapor deposition(CVD) technique, characterized by high quality growth o...Halide vapor phase epitaxy(HVPE) is widely used in the semiconductor industry for the growth of Si, GaAs, GaN, etc.HVPE is a non-organic chemical vapor deposition(CVD) technique, characterized by high quality growth of epitaxial layers with fast growth rate, which is versatile for the fabrication of both substrates and devices with wide applications. In this paper, we review the usage of HVPE for the growth and device applications of Ga_2O_3, with detailed discussions on a variety of technological aspects of HVPE. It is concluded that HVPE is a promising candidate for the epitaxy of large-area Ga_2O_3 substrates and for the fabrication of high power β-Ga_2O_3 devices.展开更多
4H-SiC single photon counting avalanche photodiodes(SPADs)are prior devices for weak ultraviolet(UV)signal detection with the advantages of small size,low leakage current,high avalanche multiplication gain,and high qu...4H-SiC single photon counting avalanche photodiodes(SPADs)are prior devices for weak ultraviolet(UV)signal detection with the advantages of small size,low leakage current,high avalanche multiplication gain,and high quantum efficiency,which benefit from the large bandgap energy,high carrier drift velocity and excellent physical stability of 4 H-SiC semiconductor material.UV detectors are widely used in many key applications,such as missile plume detection,corona discharge,UV astronomy,and biological and chemical agent detection.In this paper,we will describe basic concepts and review recent results on device design,process development,and basic characterizations of 4 H-SiC avalanche photodiodes.Several promising device structures and uniformity of avalanche multiplication are discussed,which are important for achieving high performance of 4 HSiC UV SPADs.展开更多
The 8 μm thick single-crystalline α-Ga2O3 epilayers have been heteroepitaxially grown on sapphire(0001) substrates via mist chemical vapor deposition technique. High resolution X-ray diffraction measurements show th...The 8 μm thick single-crystalline α-Ga2O3 epilayers have been heteroepitaxially grown on sapphire(0001) substrates via mist chemical vapor deposition technique. High resolution X-ray diffraction measurements show that the full-widths-at-halfmaximum(FWHM) of rocking curves for the(0006) and(10-14) planes are 0.024° and 0.24°, and the corresponding densities of screw and edge dislocations are 2.24 × 106 and 1.63 × 109 cm-2, respectively, indicative of high single crystallinity. The out-ofplane and in-plane epitaxial relationships are [0001] α-Ga2O3//[0001] α-Al2O3 and [11-20] α-Ga2O3//[11-20] α-Al2O3, respectively.The lateral domain size is in micron scale and the indirect bandgap is determined as 5.03 eV by transmittance spectra. Raman measurement indicates that the lattice-mismatch induced compressive residual strain cannot be ruled out despite the large thickness of the α-Ga2O3 epilayer. The achieved high quality α-Ga2O3 may provide an alternative material platform for developing high performance power devices and solar-blind photodetectors.展开更多
Nonpolar(1120)plane In_(x)Ga_(1-x)N epilayers comprising the entire In content(x)range were successfully grown on nanoscale Ga N islands by metal-organic chemical vapor deposition.The structural and optical properties...Nonpolar(1120)plane In_(x)Ga_(1-x)N epilayers comprising the entire In content(x)range were successfully grown on nanoscale Ga N islands by metal-organic chemical vapor deposition.The structural and optical properties were studied intensively.It was found that the surface morphology was gradually smoothed when x increased from 0.06 to 0.33,even though the crystalline quality was gradually declined,which was accompanied by the appearance of phase separation in the In_(x)Ga_(1-x)N layer.Photoluminescence wavelengths of 478 and 674 nm for blue and red light were achieved for x varied from 0.06 to 0.33.Furthermore,the corresponding average lifetime(τ_(1/e))of carriers for the nonpolar In Ga N film was decreased from 406 ps to 267 ps,indicating that a high-speed modulation bandwidth can be expected for nonpolar In Ga N-based light-emitting diodes.Moreover,the bowing coefficient(b)of the(1120)plane In Ga N was determined to be 1.91 e V for the bandgap energy as a function of x.展开更多
Self-heating effect in amorphous InGaZnO thin-film transistors remains a critical issue that degrades device performance and stability, hindering their wider applications. In this work, pulsed current–voltage analysi...Self-heating effect in amorphous InGaZnO thin-film transistors remains a critical issue that degrades device performance and stability, hindering their wider applications. In this work, pulsed current–voltage analysis has been applied to explore the physics origin of self-heating induced degradation, where Joule heat is shortly accumulated by drain current and dissipated in repeated time cycles as a function of gate bias. Enhanced positive threshold voltage shift is observed at reduced heat dissipation time, higher drain current, and increased gate width. A physical picture of Joule heating assisted charge trapping process has been proposed and then verified with pulsed negative gate bias stressing scheme, which could evidently counteract the self-heating effect through the electric-field assisted detrapping process. As a result, this pulsed gate bias scheme with negative quiescent voltage could be used as a possible way to actively suppress self-heating related device degradation.展开更多
Four 4H-SiCp-i-n ultraviolet(UV) avalanche photodiode(APD) samples PIN-0.1, PIN-0.35, PIN-0.5, and PIN-1.0 with different intrinsic layer thicknesses(0.1 μm, 0.35 μm, 0.5 μm, and 1.0 μm, respectively) are designed...Four 4H-SiCp-i-n ultraviolet(UV) avalanche photodiode(APD) samples PIN-0.1, PIN-0.35, PIN-0.5, and PIN-1.0 with different intrinsic layer thicknesses(0.1 μm, 0.35 μm, 0.5 μm, and 1.0 μm, respectively) are designed and fabricated.Single photon detection efficiency(SPDE) performance becomes better as the intrinsic layer thickness increases, which is attributed to the inhibitation of tunneling.Dark count origin is also investigated, an activation energy as small as 0.22 eV of the dark count rate(DCR) confirms that the trap-assisted tunneling(TAT) process is the main source of DCR.The temperature coefficient ranges from-2.6 mV/℃ to 18.3 mV/℃, demonstrating that the TAT process is dominant in APDs with thinner intrinsic layers.Additionally, the room temperature maximum quantum efficiency at 280 nm differs from 48% to 65% for PIN-0.35, PIN-0.5, and PIN-1.0 under 0 V bias, and UV/visible rejection ratios higher than 104 are obtained.展开更多
Ni/β-Ga_2 O_3 lateral Schottky barrier diodes(SBDs) were fabricated on a Sn-doped quasi-degenerate n^+-Ga_2 O_3(201)bulk substrate. The resultant diodes with an area of 7.85 ×10^(-5) cm^2 exhibited excellent rec...Ni/β-Ga_2 O_3 lateral Schottky barrier diodes(SBDs) were fabricated on a Sn-doped quasi-degenerate n^+-Ga_2 O_3(201)bulk substrate. The resultant diodes with an area of 7.85 ×10^(-5) cm^2 exhibited excellent rectifying characteristics with an ideality factor of 1.21, a forward current density(J) of 127.4 A/cm2 at 1.4 V, a specific on-state resistance(R_(on,sp)) of1.54 mΩ·cm^2,and an ultra-high on/off ratio of 2.1 ×10^(11) at±1 V. Due to a small depletion region in the highly-doped substrate, a breakdown feature was observed at-23 V, which corresponded to a breakdown field of 2.1 MV/cm and a power figure-of-merit(VB2/R_(on)) of 3.4×10~5 W/cm^2. Forward current-voltage characteristics were described well by the thermionic emission theory while thermionic field emission and trap-assisted tunneling were the dominant transport mechanisms at low and high reverse biases, respectively, which was a result of the contribution of deep-level traps at the metal-semiconductor interface. The presence of interfacial traps also caused the difference in Schottky barrier heights of 1.31 eV and 1.64 eV respectively determined by current-voltage and capacitance-voltage characteristics. With reduced trapping effect and incorporation of drift layers, the β-Ga_2 O_3 SBDs could further provide promising materials for delivering both high current output and high breakdown voltage.展开更多
The authors demonstrate a Bull's eye cavity design that is composed of circular Bragg gratings and micropillar optical cavity in 4H silicon carbide(4H-SiC) for single photon emission. Numerical calculations are us...The authors demonstrate a Bull's eye cavity design that is composed of circular Bragg gratings and micropillar optical cavity in 4H silicon carbide(4H-SiC) for single photon emission. Numerical calculations are used to investigate and optimize the emission rate and directionality of emission. Thanks to the optical mode resonances and Bragg reflections,the radiative decay rates of a dipole embedded in the cavity center is enhanced by 12.8 times as compared to that from a bulk 4H-SiC. In particular, a convergent angular distribution of the emission in far field is simultaneously achieved, which remarkably boost the collection efficiency. The findings of this work provide an alternative architecture to manipulate light-matter interactions for achieving high-efficient SiC single photon sources towards applications in quantum information technologies.展开更多
Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a per...Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a perfect cavity structure for such resonance to occur.Here we report GaN-based microdisks with different diameters,based on a standard blue LED wafer on a Si substrate.A confocal photoluminescence spectroscopy is performed to analyze the properties of all microdisks.Then,we systematically study the effects of radial modes and axial modes of these microdisks on photon-electron coupling efficiency by using three-dimensional finite-difference time-domain simulations.For thick microdisks,photon-electron coupling efficiency is found to greatly depend on the distributions of both the radial modes and the axial modes,and the inclined sidewalls make significant influences on the axial mode distributions.These results are important for realization of high-efficiency resonant emission in GaN-based microcavity devices.展开更多
Hybrid white micro-pillar structure light emitting diodes(LEDs)have been manufacture utilizing blue micro-LEDs arrays integrated with 580 nm CIS((CuInS2-ZnS)/ZnS)core/shell quantum dots.The fabricated hybrid white mic...Hybrid white micro-pillar structure light emitting diodes(LEDs)have been manufacture utilizing blue micro-LEDs arrays integrated with 580 nm CIS((CuInS2-ZnS)/ZnS)core/shell quantum dots.The fabricated hybrid white micro-LEDs have good electrical properties,which are manifested in relatively low turn-on voltage and reverse leakage current.High-quality hybrid white light emission has been demonstrated by the hybrid white micro-LEDs after a systemic optimization,in which the corresponding color coordinates are calculated to be(0.3303,0.3501)and the calculated color temperature is 5596 K.This result indicates an effective way to achieve high-performance white LEDs and shows great promise in a large range of applications in the future including micro-displays,bioinstrumentation and visible light communication.展开更多
Solar-blind ultraviolet(UV)photodetectors(PDs)have attracted tremendous attention in the environmental,industrial,military,and biological fields.As a representative Ill-nitride material,AlGaN alloys have broad develop...Solar-blind ultraviolet(UV)photodetectors(PDs)have attracted tremendous attention in the environmental,industrial,military,and biological fields.As a representative Ill-nitride material,AlGaN alloys have broad development prospects in the field of solar-blind detection due to their superior properties,such as tunable wide bandgaps for intrinsic UV detection.In recent decades,a variety of AlGaN-based PDs have been developed to achieve high-precision solar-blind UV detection.As integrated optoelectronic technology advances,AlGaN-based focal plane arrays(FPAs)are manufactured and exhibit outsta nding solar-blind imaging capability.Con sidering the rapid development of AlGaN detection techniques,this paper comprehensively reviews the progress on AlGaN-based solar-blind UV PDs and FPAs.First,the basic physical properties of AlGaN are presented.The epitaxy and p-type doping problems of AlGaN alloys are then discussed.Diverse PDs,including photoconductors and Schottky,metal-semiconductor-metal(MSM),p-i-n,and avalanche photodiodes(APDs),are dem on strated,and the physical mechanisms are analyzed to improve device performance.Additionally,this paper summarizes imaging technologies used with AlGaN FPAs in recent years.Benefit!ng from the development of AlGaN materials and optoelectronic devices,solar-blind UV detection technology is greeted with significant revolutions.展开更多
Monolithic white-light-emitting diodes(white LEDs) without phosphors are demonstrated using In GaN/GaN multiple quantum wells(MQWs) grown on GaN microrings formed by selective area epitaxy on SiO_2 mask patterns. The...Monolithic white-light-emitting diodes(white LEDs) without phosphors are demonstrated using In GaN/GaN multiple quantum wells(MQWs) grown on GaN microrings formed by selective area epitaxy on SiO_2 mask patterns. The microring structure is composed of {1-101} semi-polar facets and a(0001) c-plane, attributed to favorable surface polarity and surface energy. The white light is realized by combining short and long wavelengths of electroluminescence emissions from In GaN /GaN MQWs on the {1-101} semi-polar facets and the(0001) c-plane,respectively. The change in the emission wavelengths from each microfacet is due to the In composition variations of the MQWs. These results suggest that white emission can possibly be obtained without using phosphors by combining emission light from microstructures.展开更多
We fabricated p-i-n tunnel junction(TJ)contacts for hole injection on c-plane green micro-light-emitting diodes(micro-LEDs)by a hybrid growth approach using plasma-assisted molecular beam epitaxy(PA-MBE)and metal–org...We fabricated p-i-n tunnel junction(TJ)contacts for hole injection on c-plane green micro-light-emitting diodes(micro-LEDs)by a hybrid growth approach using plasma-assisted molecular beam epitaxy(PA-MBE)and metal–organic chemical vapor deposition(MOCVD).The TJ was formed by an MBE-grown ultra-thin unintentionally doped In Ga N polarization layer and an n^(++)∕n^(+)-GaN layer on the activated p^(++)-Ga N layer prepared by MOCVD.This hybrid growth approach allowed for the realization of a steep doping interface and ultrathin depletion width for efficient inter-band tunneling.Compared to standard micro-LEDs,the TJ micro-LEDs showed a reduced device resistance,enhanced electroluminescence intensity,and a reduced efficiency droop.The size-independent J-V characteristics indicate that TJ could serve as an excellent current spreading layer.All these results demonstrated that hybrid TJ contacts contributed to the realization of high-performance micro-LEDs with long emission wavelengths.展开更多
The reverse leakage characteristics of AlGaNbased ultraviolet light-emitting diodes fabricated on sapphire substrate are studied by temperature-variable current–voltage(I–V)measurement from 300 to 450 K.At low-rever...The reverse leakage characteristics of AlGaNbased ultraviolet light-emitting diodes fabricated on sapphire substrate are studied by temperature-variable current–voltage(I–V)measurement from 300 to 450 K.At low-reverse bias range(0–0.5 V),the reverse leakage current exhibits tunneling characteristics.Meanwhile,under a more negative reverse bias range([0.5 V),the log(I)–log(V)plots exhibit close-to-linear dependency,which is in good agreement with the transport mechanism of space-charge limited current.A phenomenological leakage current model focusing on electron transmission primarily through continuous defect band formed by linear defects like dislocations is suggested to explain the reverse current–voltage characteristics.展开更多
In this work, a GaN p-i-n diode based on Mg ion implantation for visible-blind UV detection is demonstrated.With an optimized implantation and annealing process, a p-GaN layer and corresponding GaN p-i-n photodiode ar...In this work, a GaN p-i-n diode based on Mg ion implantation for visible-blind UV detection is demonstrated.With an optimized implantation and annealing process, a p-GaN layer and corresponding GaN p-i-n photodiode are achieved via Mg implantation. As revealed in the UV detection characterizations, these diodes exhibit a sharp wavelength cutoff at 365 nm, high UV/visible rejection ratio of 1.2 × 10~4, and high photoresponsivity of 0.35 A/W, and are proved to be comparable with commercially available GaN p-n photodiodes. Additionally, a localized states-related gain mechanism is systematically investigated, and a relevant physics model of electricfield-assisted photocarrier hopping is proposed. The demonstrated Mg ion-implantation-based approach is believed to be an applicable and CMOS-process-compatible technology for GaN-based p-i-n photodiodes.展开更多
Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes(APDs).In this work,avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n AP...Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes(APDs).In this work,avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n APDs are compared.By studying the evolution of breakdown voltage as a function of incident light wavelength,it is confirmed that at the deep ultraviolet(UV)wavelength region the avalanche events in 4H-SiC n-i-p APDs are mainly induced by hole-initiated ionization,while electron-initiated ionization is the main cause of avalanche breakdown in 4H-SiC p-i-n APDs.Meanwhile,at the same dark count rate,the single photon counting efficiency of n-i-p APDs is considerably higher than that of p-i-n APDs.The higher performance of n-i-p APDs can be explained by the larger impact ionization coefficient of holes in 4H-SiC.In addition,this is the first time,to the best of our knowledge,to report single photon detection performance of vertical 4H-SiC n-i-p-n APDs.展开更多
Ferroelectric-semiconductor heterostructures offer an alternative strategy to manipulate polarization towards advanced devices with engineered functionality and improved performance.In this work,we report on the heter...Ferroelectric-semiconductor heterostructures offer an alternative strategy to manipulate polarization towards advanced devices with engineered functionality and improved performance.In this work,we report on the heteroepitaxial construction,band structure alignment and polarization engineering of the single-phasedκ-Ga_(2)O_(3)/GaN ferroelectric/polar heterojunction.A type-II band alignment is determined at theκ-Ga_(2)O_(3)/GaN polar hetero-interface,with a valence band offset of(1.74±0.1)eV and a conduction band offset of(0.29■0.1)eV.Besides the band edge discontinuity,charge dipoles induced by spontaneous polarization lead to the observed band bending with built-in potentials of 0.9 and 0.33 eV,respectively,at theκ-Ga_(2)O_(3)surface andκ-Ga_(2)O_(3)/GaN interface.The polarization switching properties of ferroelectricκ-Ga_(2)O_(3)are identified with a remanent polarization of approximately 2.7μC/cm^(2)via the direct hysteresis remanent polarization/voltage(P-V)loop measurement.These findings allow the rational design ofκ-Ga_(2)O_(3)ferroelectric/polar heterojunction for the application of power electronic devices,advanced memories and even ultra-low loss negative capacitance transistors.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. U2141241, 62004099, 61921005,and 91850112)。
文摘By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode(SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conduction characteristic is demonstrated by the verification of temperature-dependent current–voltage(I–V) tests and electroluminescence spectra.Meanwhile, apparently advantageous forward conduction properties as compared to the pn diode fabricated on the same wafer have been achieved, featuring a lower turn-on voltage of 0.82 V. Together with the analysis model established in the GaN SPND for a wide-range designable turn-on voltage, this work provides an alternative method to the GaN rectifier strategies besides the traditional solution.
基金supported by the National Key R&D Program of China(No.2017YFB0404201)the Solid State Lighting and Energy-Saving Electronics Collaborative Innovation Center,PAPD,and the State Grid Shandong Electric Power Company
文摘Halide vapor phase epitaxy(HVPE) is widely used in the semiconductor industry for the growth of Si, GaAs, GaN, etc.HVPE is a non-organic chemical vapor deposition(CVD) technique, characterized by high quality growth of epitaxial layers with fast growth rate, which is versatile for the fabrication of both substrates and devices with wide applications. In this paper, we review the usage of HVPE for the growth and device applications of Ga_2O_3, with detailed discussions on a variety of technological aspects of HVPE. It is concluded that HVPE is a promising candidate for the epitaxy of large-area Ga_2O_3 substrates and for the fabrication of high power β-Ga_2O_3 devices.
基金supported in part by National Key R&D Program of China under Grant No. 2016YFB0400902in part by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘4H-SiC single photon counting avalanche photodiodes(SPADs)are prior devices for weak ultraviolet(UV)signal detection with the advantages of small size,low leakage current,high avalanche multiplication gain,and high quantum efficiency,which benefit from the large bandgap energy,high carrier drift velocity and excellent physical stability of 4 H-SiC semiconductor material.UV detectors are widely used in many key applications,such as missile plume detection,corona discharge,UV astronomy,and biological and chemical agent detection.In this paper,we will describe basic concepts and review recent results on device design,process development,and basic characterizations of 4 H-SiC avalanche photodiodes.Several promising device structures and uniformity of avalanche multiplication are discussed,which are important for achieving high performance of 4 HSiC UV SPADs.
基金supported by the National Key Research and Development Project(No.2017YFB0403003)Shenzhen Fundamental Research Project(Nos.201773239,201888588)+4 种基金the National Natural Science Foundation of China(Nos.61774081,61322403)State Key Laboratory of Wide-Bandgap Semiconductor Power Electric Devices(No.2017KF001)the Natural Science Foundation of Jiangsu Province(No.BK20161401)the Six Talent Peaks Project in Jiangsu Province(Mo.2014XXRJ001)the Fundamental Research Funds for the C entral Universities(Nos.021014380093,021014380085)
文摘The 8 μm thick single-crystalline α-Ga2O3 epilayers have been heteroepitaxially grown on sapphire(0001) substrates via mist chemical vapor deposition technique. High resolution X-ray diffraction measurements show that the full-widths-at-halfmaximum(FWHM) of rocking curves for the(0006) and(10-14) planes are 0.024° and 0.24°, and the corresponding densities of screw and edge dislocations are 2.24 × 106 and 1.63 × 109 cm-2, respectively, indicative of high single crystallinity. The out-ofplane and in-plane epitaxial relationships are [0001] α-Ga2O3//[0001] α-Al2O3 and [11-20] α-Ga2O3//[11-20] α-Al2O3, respectively.The lateral domain size is in micron scale and the indirect bandgap is determined as 5.03 eV by transmittance spectra. Raman measurement indicates that the lattice-mismatch induced compressive residual strain cannot be ruled out despite the large thickness of the α-Ga2O3 epilayer. The achieved high quality α-Ga2O3 may provide an alternative material platform for developing high performance power devices and solar-blind photodetectors.
基金supported by the National Natural Science Foundation of China(Grant Nos.62074077,61921005,61974062,and 61904082)the China Postdoctoral Science Foundation(Grant No.2020M671441)+1 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant Nos.19KJB510006 and 19KJB510039)the Natural Science Foundation of Jiangsu Province(Grant No.BK20190765)。
文摘Nonpolar(1120)plane In_(x)Ga_(1-x)N epilayers comprising the entire In content(x)range were successfully grown on nanoscale Ga N islands by metal-organic chemical vapor deposition.The structural and optical properties were studied intensively.It was found that the surface morphology was gradually smoothed when x increased from 0.06 to 0.33,even though the crystalline quality was gradually declined,which was accompanied by the appearance of phase separation in the In_(x)Ga_(1-x)N layer.Photoluminescence wavelengths of 478 and 674 nm for blue and red light were achieved for x varied from 0.06 to 0.33.Furthermore,the corresponding average lifetime(τ_(1/e))of carriers for the nonpolar In Ga N film was decreased from 406 ps to 267 ps,indicating that a high-speed modulation bandwidth can be expected for nonpolar In Ga N-based light-emitting diodes.Moreover,the bowing coefficient(b)of the(1120)plane In Ga N was determined to be 1.91 e V for the bandgap energy as a function of x.
基金Project supported by the National Key R&D Program of China(Grant No.2016YFB0400100)the National Natural Science Foundation of China(Grant No.91850112)+3 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20161401)the Priority Academic Program Development of Jiangsu Higher Education Institutions,Chinathe Science and Technology Project of State Grid Corporation of China(Grant No.SGSDDK00KJJS1600071)the Fundamental Research Funds for the Central Universities,China(Grant No.14380098)
文摘Self-heating effect in amorphous InGaZnO thin-film transistors remains a critical issue that degrades device performance and stability, hindering their wider applications. In this work, pulsed current–voltage analysis has been applied to explore the physics origin of self-heating induced degradation, where Joule heat is shortly accumulated by drain current and dissipated in repeated time cycles as a function of gate bias. Enhanced positive threshold voltage shift is observed at reduced heat dissipation time, higher drain current, and increased gate width. A physical picture of Joule heating assisted charge trapping process has been proposed and then verified with pulsed negative gate bias stressing scheme, which could evidently counteract the self-heating effect through the electric-field assisted detrapping process. As a result, this pulsed gate bias scheme with negative quiescent voltage could be used as a possible way to actively suppress self-heating related device degradation.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0400902)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Four 4H-SiCp-i-n ultraviolet(UV) avalanche photodiode(APD) samples PIN-0.1, PIN-0.35, PIN-0.5, and PIN-1.0 with different intrinsic layer thicknesses(0.1 μm, 0.35 μm, 0.5 μm, and 1.0 μm, respectively) are designed and fabricated.Single photon detection efficiency(SPDE) performance becomes better as the intrinsic layer thickness increases, which is attributed to the inhibitation of tunneling.Dark count origin is also investigated, an activation energy as small as 0.22 eV of the dark count rate(DCR) confirms that the trap-assisted tunneling(TAT) process is the main source of DCR.The temperature coefficient ranges from-2.6 mV/℃ to 18.3 mV/℃, demonstrating that the TAT process is dominant in APDs with thinner intrinsic layers.Additionally, the room temperature maximum quantum efficiency at 280 nm differs from 48% to 65% for PIN-0.35, PIN-0.5, and PIN-1.0 under 0 V bias, and UV/visible rejection ratios higher than 104 are obtained.
基金supported by the National Key R&D Program of China(Grant No.2017YFB0403003)the National Natural Science Foundation of China(Grant Nos.61774081,61322403,and 91850112)+3 种基金the State Key R&D Project of Jiangsu,China(Grant No.BE2018115)Shenzhen Fundamental Research Project,China(Grant Nos.201773239 and 201888588)State Key Laboratory of Wide-Bandgap Semiconductor Power Electric Devices,China(Grant No.2017KF001)the Fundamental Research Funds for the Central Universities,China(Grant Nos.021014380093 and 021014380085)
文摘Ni/β-Ga_2 O_3 lateral Schottky barrier diodes(SBDs) were fabricated on a Sn-doped quasi-degenerate n^+-Ga_2 O_3(201)bulk substrate. The resultant diodes with an area of 7.85 ×10^(-5) cm^2 exhibited excellent rectifying characteristics with an ideality factor of 1.21, a forward current density(J) of 127.4 A/cm2 at 1.4 V, a specific on-state resistance(R_(on,sp)) of1.54 mΩ·cm^2,and an ultra-high on/off ratio of 2.1 ×10^(11) at±1 V. Due to a small depletion region in the highly-doped substrate, a breakdown feature was observed at-23 V, which corresponded to a breakdown field of 2.1 MV/cm and a power figure-of-merit(VB2/R_(on)) of 3.4×10~5 W/cm^2. Forward current-voltage characteristics were described well by the thermionic emission theory while thermionic field emission and trap-assisted tunneling were the dominant transport mechanisms at low and high reverse biases, respectively, which was a result of the contribution of deep-level traps at the metal-semiconductor interface. The presence of interfacial traps also caused the difference in Schottky barrier heights of 1.31 eV and 1.64 eV respectively determined by current-voltage and capacitance-voltage characteristics. With reduced trapping effect and incorporation of drift layers, the β-Ga_2 O_3 SBDs could further provide promising materials for delivering both high current output and high breakdown voltage.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 91850112, 61774081, 62004099, and 61921005)in part by Shenzhen Fundamental Research Program (Grant Nos. JCYJ20180307163240991 and JCYJ20180307154632609)+3 种基金in part by the State Key Research and Development Project of Jiangsu Province, China (Grant No. BE2018115)in part by the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20201253)in part by the State Key Research and Development Project of Guangdong Province, China (Grant No. 2020B010174002)in part by Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB43020500)。
文摘The authors demonstrate a Bull's eye cavity design that is composed of circular Bragg gratings and micropillar optical cavity in 4H silicon carbide(4H-SiC) for single photon emission. Numerical calculations are used to investigate and optimize the emission rate and directionality of emission. Thanks to the optical mode resonances and Bragg reflections,the radiative decay rates of a dipole embedded in the cavity center is enhanced by 12.8 times as compared to that from a bulk 4H-SiC. In particular, a convergent angular distribution of the emission in far field is simultaneously achieved, which remarkably boost the collection efficiency. The findings of this work provide an alternative architecture to manipulate light-matter interactions for achieving high-efficient SiC single photon sources towards applications in quantum information technologies.
基金the National Key R&D Program of China(Grant Nos.2016YFB0400102 and 2016YFB0400602)the National Natural Science Foundation of China(Grant Nos.61674076,61422401 and 51461135002)+2 种基金the Collaborative Innovation Center of Solid State Lighting and Energy-Saving Electronics,Open Fund of the State Key Laboratory on Integrated Optoelectronics(Grant No.IOSKL2017KF03)the Natural Science Foundation for Young Scientists of Jiangsu Province of China(Grant No.BK20160376)the Research Funds from NJU-Yangzhou Institute of Opto-electronics,and the Research and Development Funds from State Grid Shandong Electric Power Company and Electric Power Research Institute.
文摘Resonance effects caused by the photon-electron interaction are a focus of attention in semiconductor optoelectronics,as they are able to increase the efficiency of emission.GaN-on-silicon microdisks can provide a perfect cavity structure for such resonance to occur.Here we report GaN-based microdisks with different diameters,based on a standard blue LED wafer on a Si substrate.A confocal photoluminescence spectroscopy is performed to analyze the properties of all microdisks.Then,we systematically study the effects of radial modes and axial modes of these microdisks on photon-electron coupling efficiency by using three-dimensional finite-difference time-domain simulations.For thick microdisks,photon-electron coupling efficiency is found to greatly depend on the distributions of both the radial modes and the axial modes,and the inclined sidewalls make significant influences on the axial mode distributions.These results are important for realization of high-efficiency resonant emission in GaN-based microcavity devices.
基金supported by National Key R&D Program of China (2016YFB0400100)National Nature Science Foundation of China (61921005, 61674076, 61674081, 61605071, 61974062)+5 种基金Nature Science Foundation of Jiangsu Province (BY2013077, BK20141320, BE2015111)Six Talent Peaks Project of Jiangsu Province (XYDXX-081)Open Fund of the State Key Laboratory on Integrated Optoelectronics (IOSKL2017KF03)Innovation Project of Postgraduate Training in Jiangsu Province (KYCX18_0031)Fundamental Research Funds for the Central Universities (021014380096)Collaborative Innovation Center of Solid State Lighting and Energy-saving Electronics
文摘Hybrid white micro-pillar structure light emitting diodes(LEDs)have been manufacture utilizing blue micro-LEDs arrays integrated with 580 nm CIS((CuInS2-ZnS)/ZnS)core/shell quantum dots.The fabricated hybrid white micro-LEDs have good electrical properties,which are manifested in relatively low turn-on voltage and reverse leakage current.High-quality hybrid white light emission has been demonstrated by the hybrid white micro-LEDs after a systemic optimization,in which the corresponding color coordinates are calculated to be(0.3303,0.3501)and the calculated color temperature is 5596 K.This result indicates an effective way to achieve high-performance white LEDs and shows great promise in a large range of applications in the future including micro-displays,bioinstrumentation and visible light communication.
基金supported by the National Key R&D Program of China(2022YFB3605400)the State Key Research and Development Project of Guangdong(2020B010174002)the National Natural Science Foundation of China(62234007,U21A20503 and U21A2071).
基金the National Key R&D Program of China(2016YFB0400903)the NSFC(61634002),and the NSAF(U1830109).
文摘Solar-blind ultraviolet(UV)photodetectors(PDs)have attracted tremendous attention in the environmental,industrial,military,and biological fields.As a representative Ill-nitride material,AlGaN alloys have broad development prospects in the field of solar-blind detection due to their superior properties,such as tunable wide bandgaps for intrinsic UV detection.In recent decades,a variety of AlGaN-based PDs have been developed to achieve high-precision solar-blind UV detection.As integrated optoelectronic technology advances,AlGaN-based focal plane arrays(FPAs)are manufactured and exhibit outsta nding solar-blind imaging capability.Con sidering the rapid development of AlGaN detection techniques,this paper comprehensively reviews the progress on AlGaN-based solar-blind UV PDs and FPAs.First,the basic physical properties of AlGaN are presented.The epitaxy and p-type doping problems of AlGaN alloys are then discussed.Diverse PDs,including photoconductors and Schottky,metal-semiconductor-metal(MSM),p-i-n,and avalanche photodiodes(APDs),are dem on strated,and the physical mechanisms are analyzed to improve device performance.Additionally,this paper summarizes imaging technologies used with AlGaN FPAs in recent years.Benefit!ng from the development of AlGaN materials and optoelectronic devices,solar-blind UV detection technology is greeted with significant revolutions.
基金financially supported by the Natural Science Foundation of Jiangsu Province (Nos. BK20150158, BK2011436, and BM2014402)the China Postdoctoral Science Foundation (Nos. 2014M561623 and 2014M551559)+1 种基金Jiangsu Planned Projects for Postdoctoral Research Funds (No. 1401013B)the Fundamental Research Funds for Central Universities (Nos. JUSRP51517 and JUSRP11408)
文摘Monolithic white-light-emitting diodes(white LEDs) without phosphors are demonstrated using In GaN/GaN multiple quantum wells(MQWs) grown on GaN microrings formed by selective area epitaxy on SiO_2 mask patterns. The microring structure is composed of {1-101} semi-polar facets and a(0001) c-plane, attributed to favorable surface polarity and surface energy. The white light is realized by combining short and long wavelengths of electroluminescence emissions from In GaN /GaN MQWs on the {1-101} semi-polar facets and the(0001) c-plane,respectively. The change in the emission wavelengths from each microfacet is due to the In composition variations of the MQWs. These results suggest that white emission can possibly be obtained without using phosphors by combining emission light from microstructures.
基金Collaborative Innovation Center of Solid State Lighting and Energy-Saving ElectronicsLeading-Edge Technology Program of Jiangsu Natural Science Foundation(BK20202005)+1 种基金National Natural Science Foundation of China(61921005,61974062,62074077)National Key Research and Development Program of China(2017YFB0403100,2017YFB0403101)。
文摘We fabricated p-i-n tunnel junction(TJ)contacts for hole injection on c-plane green micro-light-emitting diodes(micro-LEDs)by a hybrid growth approach using plasma-assisted molecular beam epitaxy(PA-MBE)and metal–organic chemical vapor deposition(MOCVD).The TJ was formed by an MBE-grown ultra-thin unintentionally doped In Ga N polarization layer and an n^(++)∕n^(+)-GaN layer on the activated p^(++)-Ga N layer prepared by MOCVD.This hybrid growth approach allowed for the realization of a steep doping interface and ultrathin depletion width for efficient inter-band tunneling.Compared to standard micro-LEDs,the TJ micro-LEDs showed a reduced device resistance,enhanced electroluminescence intensity,and a reduced efficiency droop.The size-independent J-V characteristics indicate that TJ could serve as an excellent current spreading layer.All these results demonstrated that hybrid TJ contacts contributed to the realization of high-performance micro-LEDs with long emission wavelengths.
基金supported by the National Basic Research Program of China(2010CB327504 and 2011CB301900)the National Natural Science Foundation of China(60825401 and60936004)+1 种基金the Fundamental Research Funds for the Central Universities(JUSRP51323B)the National Science Foundation of Jiangsu Province(BK2012110)
文摘The reverse leakage characteristics of AlGaNbased ultraviolet light-emitting diodes fabricated on sapphire substrate are studied by temperature-variable current–voltage(I–V)measurement from 300 to 450 K.At low-reverse bias range(0–0.5 V),the reverse leakage current exhibits tunneling characteristics.Meanwhile,under a more negative reverse bias range([0.5 V),the log(I)–log(V)plots exhibit close-to-linear dependency,which is in good agreement with the transport mechanism of space-charge limited current.A phenomenological leakage current model focusing on electron transmission primarily through continuous defect band formed by linear defects like dislocations is suggested to explain the reverse current–voltage characteristics.
基金National Key R&D Program of China(2017YFB0403000)National Natural Science Foundation of China(NSFC)(61774081,91850112)+3 种基金Natural Science Foundation of Jiangsu Province(BK20161401)Fundamental Research Funds for the Central Universities(021014380085,021014380093,021014380098)Priority Academic Program Development of Jiangsu Higher Education InstitutionsScience and Technology Project of State Grid Corporation of China(SGSDDK00KJJS1600071)
文摘In this work, a GaN p-i-n diode based on Mg ion implantation for visible-blind UV detection is demonstrated.With an optimized implantation and annealing process, a p-GaN layer and corresponding GaN p-i-n photodiode are achieved via Mg implantation. As revealed in the UV detection characterizations, these diodes exhibit a sharp wavelength cutoff at 365 nm, high UV/visible rejection ratio of 1.2 × 10~4, and high photoresponsivity of 0.35 A/W, and are proved to be comparable with commercially available GaN p-n photodiodes. Additionally, a localized states-related gain mechanism is systematically investigated, and a relevant physics model of electricfield-assisted photocarrier hopping is proposed. The demonstrated Mg ion-implantation-based approach is believed to be an applicable and CMOS-process-compatible technology for GaN-based p-i-n photodiodes.
基金supported by the National Key R&D Program of China (No.2016YFB0400902)the National Natural Science Foundation of China (Nos.61921005 and 62004098)+1 种基金the Natural Science Foundation of Jiangsu Province (No. BK20190302)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes(APDs).In this work,avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n APDs are compared.By studying the evolution of breakdown voltage as a function of incident light wavelength,it is confirmed that at the deep ultraviolet(UV)wavelength region the avalanche events in 4H-SiC n-i-p APDs are mainly induced by hole-initiated ionization,while electron-initiated ionization is the main cause of avalanche breakdown in 4H-SiC p-i-n APDs.Meanwhile,at the same dark count rate,the single photon counting efficiency of n-i-p APDs is considerably higher than that of p-i-n APDs.The higher performance of n-i-p APDs can be explained by the larger impact ionization coefficient of holes in 4H-SiC.In addition,this is the first time,to the best of our knowledge,to report single photon detection performance of vertical 4H-SiC n-i-p-n APDs.
基金supported by the State Key Research and Development Project of Guangdong,China(Grant No.2020B010174002)the National Natural Science Foundation of China(Grant Nos.U21A20503,and U21A2071)。
文摘Ferroelectric-semiconductor heterostructures offer an alternative strategy to manipulate polarization towards advanced devices with engineered functionality and improved performance.In this work,we report on the heteroepitaxial construction,band structure alignment and polarization engineering of the single-phasedκ-Ga_(2)O_(3)/GaN ferroelectric/polar heterojunction.A type-II band alignment is determined at theκ-Ga_(2)O_(3)/GaN polar hetero-interface,with a valence band offset of(1.74±0.1)eV and a conduction band offset of(0.29■0.1)eV.Besides the band edge discontinuity,charge dipoles induced by spontaneous polarization lead to the observed band bending with built-in potentials of 0.9 and 0.33 eV,respectively,at theκ-Ga_(2)O_(3)surface andκ-Ga_(2)O_(3)/GaN interface.The polarization switching properties of ferroelectricκ-Ga_(2)O_(3)are identified with a remanent polarization of approximately 2.7μC/cm^(2)via the direct hysteresis remanent polarization/voltage(P-V)loop measurement.These findings allow the rational design ofκ-Ga_(2)O_(3)ferroelectric/polar heterojunction for the application of power electronic devices,advanced memories and even ultra-low loss negative capacitance transistors.