The design of the active region structures,including the modifications of structures of the quantum barrier(QB)and electron blocking layer(EBL),in the deep ultraviolet(DUV)Al Ga N laser diode(LD)is investigated numeri...The design of the active region structures,including the modifications of structures of the quantum barrier(QB)and electron blocking layer(EBL),in the deep ultraviolet(DUV)Al Ga N laser diode(LD)is investigated numerically with the Crosslight software.The analyses focus on electron and hole injection efficiency,electron leakage,hole diffusion,and radiative recombination rate.Compared with the reference QB structure,the step-like QB structure provides high radiative recombination and maximum output power.Subsequently,a comparative study is conducted on the performance characteristics with four different EBLs.For the EBL with different Al mole fraction layers,the higher Al-content Al Ga N EBL layer is located closely to the active region,leading the electron current leakage to lower,the carrier injection efficiency to increase,and the radiative recombination rate to improve.展开更多
The advantages of a GaN-AlGaN-InGaN last quantum barrier (LQB) in an InGaN-based blue light-emitting diode are analyzed via numerical simulation. We found an improved light output power, lower current leakage, highe...The advantages of a GaN-AlGaN-InGaN last quantum barrier (LQB) in an InGaN-based blue light-emitting diode are analyzed via numerical simulation. We found an improved light output power, lower current leakage, higher recombi- nation rate, and less efficiency droop compared with conventional GaN LQBs. These improvements in the electrical and optical characteristics are attributed mainly to the specially designed GaN-AlGaN-InGaN LQB, which enhances electron confinement and improves hole injection efficiency.展开更多
In this study, the efficiency droop of an InGaN light-emitting diode (LED) is reduced slgnlncanUy oy using a p-AlGaN/GaN superlattice last quantum barrier. The reduction in efficiency droop is mainly caused by the d...In this study, the efficiency droop of an InGaN light-emitting diode (LED) is reduced slgnlncanUy oy using a p-AlGaN/GaN superlattice last quantum barrier. The reduction in efficiency droop is mainly caused by the decrease of electron current leakage and the increase of hole injection efficiency, which is revealed by investigating the light currents, internal quantum efficiencies, energy band diagrams, carrier concentrations, carrier current densities, and radiative recombination efficiencies of three LED structures with the advanced physical model of semiconductor device (APSYS).展开更多
A multi-quantum barrier structure is employed as the electron blocking layer of light-emitting diodes to enhance their performance.Using the non-isothermal multi-physics-field coupling model,the internal quantum effic...A multi-quantum barrier structure is employed as the electron blocking layer of light-emitting diodes to enhance their performance.Using the non-isothermal multi-physics-field coupling model,the internal quantum efficiency,internal heat source characteristics,spectrum characteristics,and photoelectric conversion efficiency of light-emitting diodes are analyzed systematically.The simulation results show that:introducing multi-quantum barrier electron blocking layer structure significantly increases the internal quantum efficiency and photoelectric conversion efficiency of light-emitting diodes and the intensity of spectrum,and strongly ensures the thermal and light output stability of light-emitting diodes.These results are attributed to the modified energy band diagrams of the electron blocking layer which are responsible for the decreased electron leakage and enhanced carrier concentration in the active region.展开更多
The structural and optical properties of InGaN/GaN multiple quantum wells (MQWs) with different barrier thick-nesses are studied by means of high resolution X-ray diffraction (HRXRD), a cross-sectional transmissio...The structural and optical properties of InGaN/GaN multiple quantum wells (MQWs) with different barrier thick-nesses are studied by means of high resolution X-ray diffraction (HRXRD), a cross-sectional transmission electron mi-croscope (TEM), and temperature-dependent photoluminescence (PL) measurements. HRXRD and cross-sectional TEM measurements show that the interfaces between wells and barriers are abrupt and the entire MQW region has good periodic- ity for all three samples. As the barrier thickness is increased, the temperature of the turning point from blueshift to redshift of the S-shaped temperature-dependent PL peak energy increases monotonously, which indicates that the localization po- tentials due to In-rich clusters is deeper. From the Arrhenius plot of the normalized integrated PL intensity, it is found that there are two kinds of nonradiative recombination processes accounting for the thermal quenching of photoluminescence, and the corresponding activation energy (or the localization potential) increases with the increase of the barrier thickness. The dependence on barrier thickness is attributed to the redistribution of In-rich clusters during the growth of barrier layers, i.e., clusters with lower In contents aggregate into clusters with higher In contents.展开更多
Theories of Mott and Weertmann pertaining to quantum mechanical tunneling of dislocations from Peierls barrier in cubic crystals are revisited. Their mathematical calculations about logarithmic creep rate and lattice ...Theories of Mott and Weertmann pertaining to quantum mechanical tunneling of dislocations from Peierls barrier in cubic crystals are revisited. Their mathematical calculations about logarithmic creep rate and lattice vibrations as a manifestation of Debye temperature for quantized thermal energy are found correct but they can not ascertain to choose the mass of phonon or “quanta” of lattice vibrations. The quantum mechanical yielding in metals at relatively low temperatures, where Debye temperatures operate, is resolved and the mathematical formulas are presented. The crystal plasticity is studied with stress relaxation curves instead of logarithmic creep rate. With creep rate formulas of Mott and Weertmann, a new formula based on logarithmic profile of stress relaxation curves is proposed which suggests simultaneous quantization of dislocations with their stress, i.e., and depinning of dislocations, i.e., , where is quantum action, σ is the stress, N is the number of dislocations, A is the area and t is the time. The two different interpretations of “quantum length of Peierls barrier”, one based on curvature of space, i.e., yields quantization of Burgers vector and the other based on the curvature of time, i.e., yields depinning of dislocations from Peierls barrier in cubic crystals, are presented. , i.e., the unitary operator on shear modulus yields the variations in the curvature of time due to which simultaneous quantization, and depinning of dislocations occur from Peierls barrier in cubic crystals.展开更多
Nanoscale Schottky barrier metal oxide semiconductor field-effect transistors (MOSFETs) are explored by using quantum mechanism effects for thin-body devices. The results suggest that for small nonnegative Schottky ...Nanoscale Schottky barrier metal oxide semiconductor field-effect transistors (MOSFETs) are explored by using quantum mechanism effects for thin-body devices. The results suggest that for small nonnegative Schottky barrier heights, even for zero barrier height, the tunnelling current also plays a role in the total on-state current. Owing to the thin body of device, quantum confinement raises the electron energy levels in the silicon, and the tradeoff takes place between the quantum confinement energy and Schottky barrier lowering (SBL). It is concluded that the inclusion of the quantum mechanism effect in this model, which considers an infinite rectangular well with a first-order perturbation in the channel, can lead to the good agreement with numerical result for thin silicon film. The error increases with silicon thickness increasing.展开更多
Because of the helicity of electrons in HgTe quantum wells(QWs) with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscatt...Because of the helicity of electrons in HgTe quantum wells(QWs) with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in the HgTe QWs.This behavior is similar to Dirac electrons in graphene.In this paper,we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier.We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers.The confining effect will have a potential application in nanodevices based on HgTe QWs.展开更多
In this study we investigate strain effect in barriers of 1.3 μm AlGaInAs-InP uncooled multiple quantum welllasers.Single effective mass and Kohn-Luttinger Hamiltonian equations have been solved to obtain quantum sta...In this study we investigate strain effect in barriers of 1.3 μm AlGaInAs-InP uncooled multiple quantum welllasers.Single effective mass and Kohn-Luttinger Hamiltonian equations have been solved to obtain quantum states andenvelope wave functions in the structure.In the case of unstrained barriers,our simulations results have good agreementwith a real device fabricated and presented in one of the references.Our main work is proposal of 0.2% compressivestrain in the structure Barriers that causes significant reduction in Leakage current density and Auger current densitycharacteristics in 85℃.20% improvement in mode gain-current density characteristic is also obtained in 85℃.展开更多
We present the findings of spin-dependent single-hole and pair-hole transport in plane and across the p-type high mobility silicon quantum wells (Si-QW), 2 nm, confined by the superconductor δ-barriers on the n-type ...We present the findings of spin-dependent single-hole and pair-hole transport in plane and across the p-type high mobility silicon quantum wells (Si-QW), 2 nm, confined by the superconductor δ-barriers on the n-type Si (100) surface. The oscillations of the conductance in normal state and the zero-resistance supercurrent in superconductor state as a function of the top gate voltage are found to be correlated by on- and off-resonance tuning the two-dimensional levels of holes in Si-QW with the Fermi energy in the superconductor δ-barriers. The SIMS and STM studies have shown that the δ-barriers heavily doped with boron, 5 × 1021 cm–3, represent really alternating arrays of silicon empty and doped dots, with dimensions restricted to 2 nm. This concentration of boron seems to indicate that each doped dot located between empty dots contains two impurity atoms of boron. The EPR studies show that these boron pairs are the trigonal dipole centres, B+ - B–, that contain the pairs of holes, which result from the negative -U reconstruction of the shallow boron acceptors, 2B0 => B+ - B–. The electrical resistivity, magnetic susceptibility and specific heat measurements demonstrate that the high density of holes in the Si-QW (> 1011 cm–2) gives rise to the high temperature superconductor properties for the δ-barriers. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on- and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor δ-barriers. Finally, the proximity effect in the S-Si-QW-S structure is revealed by the findings of the quantization of the supercurrent and the multiple Andreev reflection (MAR) observed both across and along the Si-QW plane thereby identifying the spin transistor effect.展开更多
The effect of different kinds of cap layers on optical property of InAs quantum dots (QDs) on GaAs (100) substrate was studied. Temperature dependent photoluminescence (PL) indicates that the PL integrated inten...The effect of different kinds of cap layers on optical property of InAs quantum dots (QDs) on GaAs (100) substrate was studied. Temperature dependent photoluminescence (PL) indicates that the PL integrated intensity from the ground state of InAs QDs capped with an intermediate InAIAs layer drops very little as compared to QDs capped with a thin InGaAs or GaAs cap layer from 15 K up to room temperature. PL integrated intensity ratio of the first excited to ground states for InAs QDs capped with an intermediate InAIAs layer is unexpectedly decreased with increasing temperature, which are attributed to phonon bottleneck effect. A virtual barrier is proposed to describe this physics process and shows good agreement with experimental results when fitting the curve with the value of the virtual barrier 30 meV.展开更多
In this study, the characteristics of nitride-based light-emitting diodes with different last barrier structures are analysed numerically. The energy band diagrams, electrostatic field near the last quantum barrier, c...In this study, the characteristics of nitride-based light-emitting diodes with different last barrier structures are analysed numerically. The energy band diagrams, electrostatic field near the last quantum barrier, carrier concentration in the quantum well, internal quantum efficiency, and light output power are systematically investigated. The simulation results show that the efficiency droop is markedly improved and the output power is greatly enhanced when the conventional GaN last barrier is replaced by an AlGaN barrier with Al composition graded linearly from 0 to 15% in the growth direction. These improvements are attributed to enhanced efficiencies of electron confinement and hole injection caused by the lower polarization effect at the last-barrier/electron blocking layer interface when the graded Al composition last barrier is used.展开更多
基金Project supported by the Special Project for Inter-government Collaboration of State Key Research and Development Program,China(Grant No.2016YFE0118400)the Key Project of Science and Technology of Henan Province,China(Grant No.172102410062)the National Natural Science Foundation of China and Henan Provincial Joint Fund Key Project(Grant No.U1604263)
文摘The design of the active region structures,including the modifications of structures of the quantum barrier(QB)and electron blocking layer(EBL),in the deep ultraviolet(DUV)Al Ga N laser diode(LD)is investigated numerically with the Crosslight software.The analyses focus on electron and hole injection efficiency,electron leakage,hole diffusion,and radiative recombination rate.Compared with the reference QB structure,the step-like QB structure provides high radiative recombination and maximum output power.Subsequently,a comparative study is conducted on the performance characteristics with four different EBLs.For the EBL with different Al mole fraction layers,the higher Al-content Al Ga N EBL layer is located closely to the active region,leading the electron current leakage to lower,the carrier injection efficiency to increase,and the radiative recombination rate to improve.
基金Project supported by the Special Strategic Emerging Industries of Guangdong Province,China(Grant Nos.2011A081301004 and 2012A080304006)
文摘The advantages of a GaN-AlGaN-InGaN last quantum barrier (LQB) in an InGaN-based blue light-emitting diode are analyzed via numerical simulation. We found an improved light output power, lower current leakage, higher recombi- nation rate, and less efficiency droop compared with conventional GaN LQBs. These improvements in the electrical and optical characteristics are attributed mainly to the specially designed GaN-AlGaN-InGaN LQB, which enhances electron confinement and improves hole injection efficiency.
基金Project supported by the National Natural Science Foundation of China(Grant No.61176043)the Special Funds for Provincial Strategic and Emerging Industries Projects of Guangdong Province,China(Grant Nos.2010A081002005,2011A081301003,and 2012A080304016)+2 种基金the First Phase of Construction of Guangdong Research Institute of Semiconductor Lighting Industrial Technology,China(Grant No.2010A081001001)the High Efficiency LED Epitaxy and Chip Structure and Key Technology for Industrialization,China(Grant No.2012A080302002)the Youth Funding of South China Normal University(Grant No.2012KJ018)
文摘In this study, the efficiency droop of an InGaN light-emitting diode (LED) is reduced slgnlncanUy oy using a p-AlGaN/GaN superlattice last quantum barrier. The reduction in efficiency droop is mainly caused by the decrease of electron current leakage and the increase of hole injection efficiency, which is revealed by investigating the light currents, internal quantum efficiencies, energy band diagrams, carrier concentrations, carrier current densities, and radiative recombination efficiencies of three LED structures with the advanced physical model of semiconductor device (APSYS).
基金supported by the National Natural Science Foundation of China (U1034004 and 50825603)the National Basic Research Program of China (2011CB710703)the Fundamental Research Funds for the Central University (11ZG01)
文摘A multi-quantum barrier structure is employed as the electron blocking layer of light-emitting diodes to enhance their performance.Using the non-isothermal multi-physics-field coupling model,the internal quantum efficiency,internal heat source characteristics,spectrum characteristics,and photoelectric conversion efficiency of light-emitting diodes are analyzed systematically.The simulation results show that:introducing multi-quantum barrier electron blocking layer structure significantly increases the internal quantum efficiency and photoelectric conversion efficiency of light-emitting diodes and the intensity of spectrum,and strongly ensures the thermal and light output stability of light-emitting diodes.These results are attributed to the modified energy band diagrams of the electron blocking layer which are responsible for the decreased electron leakage and enhanced carrier concentration in the active region.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61106044 and 61274052)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110121110029)+1 种基金the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.2013121024)the Natural Science Foundation of Fujian Province of China(Grant No.2013J05096)
文摘The structural and optical properties of InGaN/GaN multiple quantum wells (MQWs) with different barrier thick-nesses are studied by means of high resolution X-ray diffraction (HRXRD), a cross-sectional transmission electron mi-croscope (TEM), and temperature-dependent photoluminescence (PL) measurements. HRXRD and cross-sectional TEM measurements show that the interfaces between wells and barriers are abrupt and the entire MQW region has good periodic- ity for all three samples. As the barrier thickness is increased, the temperature of the turning point from blueshift to redshift of the S-shaped temperature-dependent PL peak energy increases monotonously, which indicates that the localization po- tentials due to In-rich clusters is deeper. From the Arrhenius plot of the normalized integrated PL intensity, it is found that there are two kinds of nonradiative recombination processes accounting for the thermal quenching of photoluminescence, and the corresponding activation energy (or the localization potential) increases with the increase of the barrier thickness. The dependence on barrier thickness is attributed to the redistribution of In-rich clusters during the growth of barrier layers, i.e., clusters with lower In contents aggregate into clusters with higher In contents.
文摘Theories of Mott and Weertmann pertaining to quantum mechanical tunneling of dislocations from Peierls barrier in cubic crystals are revisited. Their mathematical calculations about logarithmic creep rate and lattice vibrations as a manifestation of Debye temperature for quantized thermal energy are found correct but they can not ascertain to choose the mass of phonon or “quanta” of lattice vibrations. The quantum mechanical yielding in metals at relatively low temperatures, where Debye temperatures operate, is resolved and the mathematical formulas are presented. The crystal plasticity is studied with stress relaxation curves instead of logarithmic creep rate. With creep rate formulas of Mott and Weertmann, a new formula based on logarithmic profile of stress relaxation curves is proposed which suggests simultaneous quantization of dislocations with their stress, i.e., and depinning of dislocations, i.e., , where is quantum action, σ is the stress, N is the number of dislocations, A is the area and t is the time. The two different interpretations of “quantum length of Peierls barrier”, one based on curvature of space, i.e., yields quantization of Burgers vector and the other based on the curvature of time, i.e., yields depinning of dislocations from Peierls barrier in cubic crystals, are presented. , i.e., the unitary operator on shear modulus yields the variations in the curvature of time due to which simultaneous quantization, and depinning of dislocations occur from Peierls barrier in cubic crystals.
基金Project supported by the National Natural Science Foundation of China (Grant No 60206006)the Program for New Century Excellent Talents of Ministry of Education of China (Grant No NCET-05-085)the Xi'an Applied Materials Innovation Fund (Grant No XA-AM-200701)
文摘Nanoscale Schottky barrier metal oxide semiconductor field-effect transistors (MOSFETs) are explored by using quantum mechanism effects for thin-body devices. The results suggest that for small nonnegative Schottky barrier heights, even for zero barrier height, the tunnelling current also plays a role in the total on-state current. Owing to the thin body of device, quantum confinement raises the electron energy levels in the silicon, and the tradeoff takes place between the quantum confinement energy and Schottky barrier lowering (SBL). It is concluded that the inclusion of the quantum mechanism effect in this model, which considers an infinite rectangular well with a first-order perturbation in the channel, can lead to the good agreement with numerical result for thin silicon film. The error increases with silicon thickness increasing.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10821403 and 11047131)the National Basic Research Program of China(Grant No. 2009CB929100)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20101303120005)
文摘Because of the helicity of electrons in HgTe quantum wells(QWs) with inverted band structures,the electrons cannot be confined by electric barriers since electrons can tunnel the barriers perfectly without backscattering in the HgTe QWs.This behavior is similar to Dirac electrons in graphene.In this paper,we propose a scheme to confine carriers in HgTe QWs using an electric-magnetic barrier.We calculate the transmission of carriers in 2-dimensional HgTe QWs and find that the wave-vector filtering effect of local magnetic fields can confine the carriers.The confining effect will have a potential application in nanodevices based on HgTe QWs.
文摘In this study we investigate strain effect in barriers of 1.3 μm AlGaInAs-InP uncooled multiple quantum welllasers.Single effective mass and Kohn-Luttinger Hamiltonian equations have been solved to obtain quantum states andenvelope wave functions in the structure.In the case of unstrained barriers,our simulations results have good agreementwith a real device fabricated and presented in one of the references.Our main work is proposal of 0.2% compressivestrain in the structure Barriers that causes significant reduction in Leakage current density and Auger current densitycharacteristics in 85℃.20% improvement in mode gain-current density characteristic is also obtained in 85℃.
文摘We present the findings of spin-dependent single-hole and pair-hole transport in plane and across the p-type high mobility silicon quantum wells (Si-QW), 2 nm, confined by the superconductor δ-barriers on the n-type Si (100) surface. The oscillations of the conductance in normal state and the zero-resistance supercurrent in superconductor state as a function of the top gate voltage are found to be correlated by on- and off-resonance tuning the two-dimensional levels of holes in Si-QW with the Fermi energy in the superconductor δ-barriers. The SIMS and STM studies have shown that the δ-barriers heavily doped with boron, 5 × 1021 cm–3, represent really alternating arrays of silicon empty and doped dots, with dimensions restricted to 2 nm. This concentration of boron seems to indicate that each doped dot located between empty dots contains two impurity atoms of boron. The EPR studies show that these boron pairs are the trigonal dipole centres, B+ - B–, that contain the pairs of holes, which result from the negative -U reconstruction of the shallow boron acceptors, 2B0 => B+ - B–. The electrical resistivity, magnetic susceptibility and specific heat measurements demonstrate that the high density of holes in the Si-QW (> 1011 cm–2) gives rise to the high temperature superconductor properties for the δ-barriers. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on- and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor δ-barriers. Finally, the proximity effect in the S-Si-QW-S structure is revealed by the findings of the quantization of the supercurrent and the multiple Andreev reflection (MAR) observed both across and along the Si-QW plane thereby identifying the spin transistor effect.
文摘The effect of different kinds of cap layers on optical property of InAs quantum dots (QDs) on GaAs (100) substrate was studied. Temperature dependent photoluminescence (PL) indicates that the PL integrated intensity from the ground state of InAs QDs capped with an intermediate InAIAs layer drops very little as compared to QDs capped with a thin InGaAs or GaAs cap layer from 15 K up to room temperature. PL integrated intensity ratio of the first excited to ground states for InAs QDs capped with an intermediate InAIAs layer is unexpectedly decreased with increasing temperature, which are attributed to phonon bottleneck effect. A virtual barrier is proposed to describe this physics process and shows good agreement with experimental results when fitting the curve with the value of the virtual barrier 30 meV.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1034004 and 50825603)the Fundamental Research Funds for the Central Universities,China(Grant Nos.12QX14 and 11ZG01)
文摘In this study, the characteristics of nitride-based light-emitting diodes with different last barrier structures are analysed numerically. The energy band diagrams, electrostatic field near the last quantum barrier, carrier concentration in the quantum well, internal quantum efficiency, and light output power are systematically investigated. The simulation results show that the efficiency droop is markedly improved and the output power is greatly enhanced when the conventional GaN last barrier is replaced by an AlGaN barrier with Al composition graded linearly from 0 to 15% in the growth direction. These improvements are attributed to enhanced efficiencies of electron confinement and hole injection caused by the lower polarization effect at the last-barrier/electron blocking layer interface when the graded Al composition last barrier is used.