Homoepitaxial growth of Si-doped β-Ga_(2)O_(3) films on semi-insulating(100) β-Ga_(2)O_(3) substrates by metalorganic chemical vapor deposition(MOCVD) is studied in this work. By appropriately optimizing the growth ...Homoepitaxial growth of Si-doped β-Ga_(2)O_(3) films on semi-insulating(100) β-Ga_(2)O_(3) substrates by metalorganic chemical vapor deposition(MOCVD) is studied in this work. By appropriately optimizing the growth conditions, an increasing diffusion length of Ga adatoms is realized, suppressing 3D island growth patterns prevalent in(100) β-Ga_(2)O_(3) films and optimizing the surface morphology with [010] oriented stripe features. The slightly Si-doped β-Ga_(2)O_(3) film shows smooth and flat surface morphology with a root-mean-square roughness of 1.3 nm. Rocking curves of the(400) diffraction peak also demonstrate the high crystal quality of the Si-doped films. According to the capacitance–voltage characteristics, the effective net doping concentrations of the films are 5.41 × 10~(15) – 1.74 × 10~(20) cm~(-3). Hall measurements demonstrate a high electron mobility value of 51cm~2/(V·s), corresponding to a carrier concentration of 7.19 × 10~(18) cm~(-3) and a high activation efficiency of up to 61.5%. Transmission line model(TLM) measurement shows excellent Ohmic contacts and a low specific contact resistance of 1.29 × 10~(-4) Ω·cm~2 for the Si-doped film, which is comparable to the Si-implanted film with a concentration of 5.0 × 10~(19) cm~(-3), confirming the effective Si doing in the MOCVD epitaxy.展开更多
The high power GaN-based blue light emitting diode (LED) on an 80%tm-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition (MOCVD), hydride vapo...The high power GaN-based blue light emitting diode (LED) on an 80%tm-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition (MOCVD), hydride vapor-phase epi- taxial (HVPE), and laser lift-off (LLO). Its advantages are demonstrated from material quality and chip processing. It is investigated by high resolution X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Rutherford back-scattering (RBS), photoluminescence, current-voltage and light output-current measurements. The width of (0002) reflection in XRD rocking curve, which reaches 173" for the thick GaN template LED, is less than that for the conventional one, which reaches 258". The HRTEM images show that the multiple quantum wells (MQWs) in 80%tm- thick GaN template LED have a generally higher crystal quality. The light output at 350 mA from the thick GaN template LED is doubled compared to traditional LEDs and the forward bias is also substantially reduced. The high performance of 80-~m-thick GaN template LED depends on the high crystal quality. However, although the intensity of MQWs emission in PL spectra is doubled, both the wavelength and the width of the emission from thick GaN template LED are increased. This is due to the strain relaxation on the surface of 80%tin-thick GaN template, which changes the strain in InGaN QWs and leads to InGaN phase separation.展开更多
Chloride-based fast homoepitaxial growth of 4H-SiC epilayers was performed on 4° off-axis 4H-SiC substrates in a home-made vertical hot-wall chemical vapor deposition(CVD) system using H2-SiH4-C2H4-HCl.The effe...Chloride-based fast homoepitaxial growth of 4H-SiC epilayers was performed on 4° off-axis 4H-SiC substrates in a home-made vertical hot-wall chemical vapor deposition(CVD) system using H2-SiH4-C2H4-HCl.The effect of the SiH_4/H_2 ratio and reactor pressure on the growth rate of 4H-SiC epilayers has been studied successively.The growth rate increase in proportion to the SiH_4/H_2 ratio and the influence mechanism of chlorine has been investigated.With the reactor pressure increasing from 40 to 100 Torr,the growth rate increased to 52μm/h and then decreased to 47 μm/h,which is due to the joint effect of H_2 and HC1 etching as well as the formation of Si clusters at higher reactor pressure.The surface root mean square(RMS) roughness keeps around 1 nm with the growth rate increasing to 49 μm/h.The scanning electron microscope(SEM),Raman spectroscopy and X-ray diffraction(XRD) demonstrate that 96.7 μm thick 4H-SiC layers of good uniformity in thickness and doping with high crystal quality can be achieved.These results prove that chloride-based fast epitaxy is an advanced growth technique for 4H-SiC homoepitaxy.展开更多
High quality,homoepitaxial layers of 4H-SiC were grown on off-oriented 4H-SiC(0001) Si planes in a vertical low-pressure hot-wall CVD system(LPCVD) by using trichlorosilane(TCS) as a silicon precursor source tog...High quality,homoepitaxial layers of 4H-SiC were grown on off-oriented 4H-SiC(0001) Si planes in a vertical low-pressure hot-wall CVD system(LPCVD) by using trichlorosilane(TCS) as a silicon precursor source together with ethylene(C;H;) as a carbon precursor source.The growth rate of 25-30μm/h has been achieved at lower temperatures between 1500 and 1530℃.The surface roughness and crystalline quality of 50μm thick epitaxial layers(grown for 2 h) did not deteriorate compared with the corresponding results of thinner layers(grown for 30 min).The background doping concentration was reduced to 2.13×10;cm;.The effect of the C/Si ratio in the gas phase on growth rate and quality of the epi-layers was investigated.展开更多
Unintentionally doped 4H-SiC homoepitaxial layers grown by hot-wall chemical vapor deposition (HWCVD) have been studied using photoluminescence (PL) technique in the temperature range of 10 to 240 K. A broadband g...Unintentionally doped 4H-SiC homoepitaxial layers grown by hot-wall chemical vapor deposition (HWCVD) have been studied using photoluminescence (PL) technique in the temperature range of 10 to 240 K. A broadband green luminescence has been observed. Vacancies of carbon (Vc) are revealed by electron spin resonance (ESR) technique at 110 K. The results strongly suggest that the green band luminescence, as shallow donor-deep accepter emission, is attributed to the vacancies of C and the extended defects. The broadband green luminescence spectrum can be fitted by the two Gauss-type spectra using nonlinear optimization technique. It shows that the broad-band green luminescence originates from the combination of two independent radiative transitions. The centers of two energy levels are located 2.378 and 2.130 eV below the conduction band, respectively, and the ends of two energy levels are expanded and superimposed each other.展开更多
In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage(I–V –T) characteristics of a Schottky barrier diode fabricated on free...In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage(I–V –T) characteristics of a Schottky barrier diode fabricated on free-standing GaN substrate for reverse-bias voltages up to-150 V. The model suggests that the reverse leakage current is dominated by the direct tunneling of electrons from Schottky contact metal into a continuum of states associated with conductive dislocations in GaN epilayer.A reverse leakage current ideality factor, which originates from the scattering effect at metal/GaN interface, is introduced into the model. Good agreement between the experimental data and the simulated I–V curves is obtained.展开更多
The homoepitaxial growth of multilayer Si thin film on Si(111) surfaces was simulated by Monte Carlo (MC) method with realistic growth model and physical parameters. Special emphasis was placed on revealing the influe...The homoepitaxial growth of multilayer Si thin film on Si(111) surfaces was simulated by Monte Carlo (MC) method with realistic growth model and physical parameters. Special emphasis was placed on revealing the influence of the Ehrlich-Schwoebel (ES) barrier on the growth modes and morphologies. It is evident that there exists the ES barrier during multilayer Si thin film growth on Si (111) surface, which is deduced from the incomplete layer-by-layer growth process in the realistic experiments. The ES barrier EB=0.1~0.125 eV is estimated from the three-dimensional (3D) MC simulation and compared with the experimental results.展开更多
Pit formation and surface morphological evolution in Si(001) homoepitaxy are investigated by using scanning tunneling microscopy. Anti-phase boundary is found to give rise to initial generation of pits bound by bunc...Pit formation and surface morphological evolution in Si(001) homoepitaxy are investigated by using scanning tunneling microscopy. Anti-phase boundary is found to give rise to initial generation of pits bound by bunched DB steps. The terraces break up and are reduced to a critical nucleus size with pit formation. Due to anisotropic kinetics, a downhill bias diffusion current, which is larger along the dimer rows through the centre area of the terrace than through the area close to the edge, leads to the prevalence of pits bound by {101} facets. Subsequent annealing results in a shape transition from {101)-faceted pits to multi-faceted pits.展开更多
With H<sub>2</sub> and CH<sub>3</sub>COCH<sub>3</sub> used as the source gases,the diamond epitaxlal films were obtained on the sythe siged single-crystal diamond(100),(110)and...With H<sub>2</sub> and CH<sub>3</sub>COCH<sub>3</sub> used as the source gases,the diamond epitaxlal films were obtained on the sythe siged single-crystal diamond(100),(110)and(111)faces by means of the microwave plasma-assisted chemical-vapor-deposition (CVD) method. Epitaxlal growth spirals and growth steps can be observed by scanning electron micrographs. Using micro Raman spectra method,we analysed the contents of graphites and other forms of carbon in the single-crystal diamond thin films.The experimental results showed that there are no other forms of carbon in the epitaxial films.Analysis results of reflection electron diffraction showed that the epitaxial diainond film s on diamond(100)an(110)Surfaces are single-crystal diamond films.展开更多
基金supported in part by the National Basic Research Program of China (Grant No. 2021YFB3600202)Key Laboratory Construction Project of Nanchang (Grant No. 2020-NCZDSY-008)Suzhou Science and Technology Foundation (Grant No. SYG202027)。
文摘Homoepitaxial growth of Si-doped β-Ga_(2)O_(3) films on semi-insulating(100) β-Ga_(2)O_(3) substrates by metalorganic chemical vapor deposition(MOCVD) is studied in this work. By appropriately optimizing the growth conditions, an increasing diffusion length of Ga adatoms is realized, suppressing 3D island growth patterns prevalent in(100) β-Ga_(2)O_(3) films and optimizing the surface morphology with [010] oriented stripe features. The slightly Si-doped β-Ga_(2)O_(3) film shows smooth and flat surface morphology with a root-mean-square roughness of 1.3 nm. Rocking curves of the(400) diffraction peak also demonstrate the high crystal quality of the Si-doped films. According to the capacitance–voltage characteristics, the effective net doping concentrations of the films are 5.41 × 10~(15) – 1.74 × 10~(20) cm~(-3). Hall measurements demonstrate a high electron mobility value of 51cm~2/(V·s), corresponding to a carrier concentration of 7.19 × 10~(18) cm~(-3) and a high activation efficiency of up to 61.5%. Transmission line model(TLM) measurement shows excellent Ohmic contacts and a low specific contact resistance of 1.29 × 10~(-4) Ω·cm~2 for the Si-doped film, which is comparable to the Si-implanted film with a concentration of 5.0 × 10~(19) cm~(-3), confirming the effective Si doing in the MOCVD epitaxy.
基金Project supported by the National Basic Research Foundation of China (Grant Nos. TG2011CB301905 and TG2012CB619304) and the National Natural Science Foundation of China (Grant Nos. 60876063 and 61076012).
文摘The high power GaN-based blue light emitting diode (LED) on an 80%tm-thick GaN template is proposed and even realized by several technical methods like metal organic chemical vapor deposition (MOCVD), hydride vapor-phase epi- taxial (HVPE), and laser lift-off (LLO). Its advantages are demonstrated from material quality and chip processing. It is investigated by high resolution X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), Rutherford back-scattering (RBS), photoluminescence, current-voltage and light output-current measurements. The width of (0002) reflection in XRD rocking curve, which reaches 173" for the thick GaN template LED, is less than that for the conventional one, which reaches 258". The HRTEM images show that the multiple quantum wells (MQWs) in 80%tm- thick GaN template LED have a generally higher crystal quality. The light output at 350 mA from the thick GaN template LED is doubled compared to traditional LEDs and the forward bias is also substantially reduced. The high performance of 80-~m-thick GaN template LED depends on the high crystal quality. However, although the intensity of MQWs emission in PL spectra is doubled, both the wavelength and the width of the emission from thick GaN template LED are increased. This is due to the strain relaxation on the surface of 80%tin-thick GaN template, which changes the strain in InGaN QWs and leads to InGaN phase separation.
基金supported by the National High Technology R&D Program of China(No.2014AA041402)the National Natural Science Foundation of China(Nos.61474113,61274007,61574140)+2 种基金the Beijing Natural Science Foundation of China(Nos.4132076,4132074)the Program of State Grid Smart Grid Research Institute(No.SGRI-WD-71-14-004)the Youth Innovation Promotion Association of CAS
文摘Chloride-based fast homoepitaxial growth of 4H-SiC epilayers was performed on 4° off-axis 4H-SiC substrates in a home-made vertical hot-wall chemical vapor deposition(CVD) system using H2-SiH4-C2H4-HCl.The effect of the SiH_4/H_2 ratio and reactor pressure on the growth rate of 4H-SiC epilayers has been studied successively.The growth rate increase in proportion to the SiH_4/H_2 ratio and the influence mechanism of chlorine has been investigated.With the reactor pressure increasing from 40 to 100 Torr,the growth rate increased to 52μm/h and then decreased to 47 μm/h,which is due to the joint effect of H_2 and HC1 etching as well as the formation of Si clusters at higher reactor pressure.The surface root mean square(RMS) roughness keeps around 1 nm with the growth rate increasing to 49 μm/h.The scanning electron microscope(SEM),Raman spectroscopy and X-ray diffraction(XRD) demonstrate that 96.7 μm thick 4H-SiC layers of good uniformity in thickness and doping with high crystal quality can be achieved.These results prove that chloride-based fast epitaxy is an advanced growth technique for 4H-SiC homoepitaxy.
基金Project supported by the National Natural Science Foundation of China(No60876003)the Chinese Academy of Sciences(No Y072011000)+1 种基金the Beijing Municipal Science & Technology Commission(NoD09080300500903)the Knowledge Innovation Program of the Chinese Academy of Sciences(NoISCAS2008T04)
文摘High quality,homoepitaxial layers of 4H-SiC were grown on off-oriented 4H-SiC(0001) Si planes in a vertical low-pressure hot-wall CVD system(LPCVD) by using trichlorosilane(TCS) as a silicon precursor source together with ethylene(C;H;) as a carbon precursor source.The growth rate of 25-30μm/h has been achieved at lower temperatures between 1500 and 1530℃.The surface roughness and crystalline quality of 50μm thick epitaxial layers(grown for 2 h) did not deteriorate compared with the corresponding results of thinner layers(grown for 30 min).The background doping concentration was reduced to 2.13×10;cm;.The effect of the C/Si ratio in the gas phase on growth rate and quality of the epi-layers was investigated.
基金supported by the State Key Development Program for Basic Research of China (No. 51327020202)the Key Fund of the Ministryof Education of China (No. 106150)the Xi’an Applied Materials Innovation Fund (No. XA-AM-200607).
文摘Unintentionally doped 4H-SiC homoepitaxial layers grown by hot-wall chemical vapor deposition (HWCVD) have been studied using photoluminescence (PL) technique in the temperature range of 10 to 240 K. A broadband green luminescence has been observed. Vacancies of carbon (Vc) are revealed by electron spin resonance (ESR) technique at 110 K. The results strongly suggest that the green band luminescence, as shallow donor-deep accepter emission, is attributed to the vacancies of C and the extended defects. The broadband green luminescence spectrum can be fitted by the two Gauss-type spectra using nonlinear optimization technique. It shows that the broad-band green luminescence originates from the combination of two independent radiative transitions. The centers of two energy levels are located 2.378 and 2.130 eV below the conduction band, respectively, and the ends of two energy levels are expanded and superimposed each other.
文摘In this work, a dislocation-related tunneling leakage current model is developed to explain the temperature-dependent reverse current–voltage(I–V –T) characteristics of a Schottky barrier diode fabricated on free-standing GaN substrate for reverse-bias voltages up to-150 V. The model suggests that the reverse leakage current is dominated by the direct tunneling of electrons from Schottky contact metal into a continuum of states associated with conductive dislocations in GaN epilayer.A reverse leakage current ideality factor, which originates from the scattering effect at metal/GaN interface, is introduced into the model. Good agreement between the experimental data and the simulated I–V curves is obtained.
基金Project supported by the Natural Science Foundation for Young Scientists of Zhejiang Province (RC02069)
文摘The homoepitaxial growth of multilayer Si thin film on Si(111) surfaces was simulated by Monte Carlo (MC) method with realistic growth model and physical parameters. Special emphasis was placed on revealing the influence of the Ehrlich-Schwoebel (ES) barrier on the growth modes and morphologies. It is evident that there exists the ES barrier during multilayer Si thin film growth on Si (111) surface, which is deduced from the incomplete layer-by-layer growth process in the realistic experiments. The ES barrier EB=0.1~0.125 eV is estimated from the three-dimensional (3D) MC simulation and compared with the experimental results.
基金Project supported by the grants from the National University of Singapore (R-144-000-069-101)the SERC of Singapore(R-144-000-088-305)
文摘Pit formation and surface morphological evolution in Si(001) homoepitaxy are investigated by using scanning tunneling microscopy. Anti-phase boundary is found to give rise to initial generation of pits bound by bunched DB steps. The terraces break up and are reduced to a critical nucleus size with pit formation. Due to anisotropic kinetics, a downhill bias diffusion current, which is larger along the dimer rows through the centre area of the terrace than through the area close to the edge, leads to the prevalence of pits bound by {101} facets. Subsequent annealing results in a shape transition from {101)-faceted pits to multi-faceted pits.
文摘With H<sub>2</sub> and CH<sub>3</sub>COCH<sub>3</sub> used as the source gases,the diamond epitaxlal films were obtained on the sythe siged single-crystal diamond(100),(110)and(111)faces by means of the microwave plasma-assisted chemical-vapor-deposition (CVD) method. Epitaxlal growth spirals and growth steps can be observed by scanning electron micrographs. Using micro Raman spectra method,we analysed the contents of graphites and other forms of carbon in the single-crystal diamond thin films.The experimental results showed that there are no other forms of carbon in the epitaxial films.Analysis results of reflection electron diffraction showed that the epitaxial diainond film s on diamond(100)an(110)Surfaces are single-crystal diamond films.