Two-inch Ga_2O_3 films with(ˉ201)-orientation are grown on c-sapphire at 850–1050°C by hydride vapor phase epitaxy. High-resolution x-ray diffraction shows that pure β-Ga_2O_3 with a smooth surface has a hig...Two-inch Ga_2O_3 films with(ˉ201)-orientation are grown on c-sapphire at 850–1050°C by hydride vapor phase epitaxy. High-resolution x-ray diffraction shows that pure β-Ga_2O_3 with a smooth surface has a higher crystal quality, and the Raman spectra reveal a very small residual strain in β-Ga_2O_3 grown by hydride vapor phase epitaxy compared with bulk single crystal. The optical transmittance is higher than 80% in the visible and near-UV regions, and the optical bandgap energy is calculated to be 4.9 e V.展开更多
GaN-based micro light emitting diodes(micro-LEDs) on silicon(Si)substrates with 40μm in diameter are developed utilizing standard photolithography and inductively coupled plasma etching techniques.From currentvoltage...GaN-based micro light emitting diodes(micro-LEDs) on silicon(Si)substrates with 40μm in diameter are developed utilizing standard photolithography and inductively coupled plasma etching techniques.From currentvoltage curves,the relatively low turn-on voltage of 2.8 V and low reverse leakage current in the order of 10-8 A/cm2 indicate good electrical characteristics.As the injection current increases,the electroluminescence emission wavelength hardly shifts at around 433 nm, and the relative external quantum efficiency slightly decays,because the impact of quantum-confined Stark effect is not serious in violet-blue micro-LEDs.Since GaN-LEDs are cost effective on large-area Si and suitable for substrate transfer or vertical device structures,the fabricated micro-LEDs on Si should have promising applications in the fields of high-resolution display and optical communication.展开更多
The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration(~ 1020 cm-3) grown by metal–organic chemical vapor deposition(MOCVD) are systematically studied thro...The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration(~ 1020 cm-3) grown by metal–organic chemical vapor deposition(MOCVD) are systematically studied through optical and electrical properties. Emission lines of shallow oxygen donors and(VⅢ complex)1- as well as VN3+ and neutral Mg acceptors are observed, which indicate that self-compensation is occurred in Mg-doped AlGaN at highly doping levels. The fitting of the temperature-dependent Hall effect data shows that the acceptor activation energy values in Mgdoped AlxGa1-xN(x = 0.23, 0.35) are 172 meV and 242 meV, and the hole concentrations at room temperature are 1.2×1018 cm-3 and 3.3× 1017 cm-3, respectively. Therefore, it is believed that there exists the combined effect of the Coulomb potentials of the dopants and screening of the Coulomb potentials by a high hole concentration. Moreover, due to the high ionized acceptors’ concentration and compensation ratio, the impurity conduction becomes more prominent and the valence band mobility drops sharply at low temperature.展开更多
A systematic investigation on PA-MBE grown GaN with low growth rates(less than 0.2μm/h)has been conducted in a wide growth temperature range,in order to guide future growth of sophisticated fine structures for quantu...A systematic investigation on PA-MBE grown GaN with low growth rates(less than 0.2μm/h)has been conducted in a wide growth temperature range,in order to guide future growth of sophisticated fine structures for quantum device applications.Similar to usual growths with higher growth rates,three growth regions have been revealed,namely,Ga droplets,slightly Ga-rich and N-rich 3D growth regions.The slightly Ga-rich region is preferred,in which GaN epilayers demonstrate optimal crystalline quality,which has been demonstrated by streaky RHEED patterns,atomic smooth surface morphology,and very low defect related yellow and blue luminescence bands.The growth temperature is a critical parameter to obtain high quality materials and the optimal growth temperature window(~700-760℃)has been identified.The growth rate shows a strong dependence on growth temperatures in the optimal temperature window,and attention must be paid when growing fine structures at a low growth rate.Mg and Si doped GaN were also studied,and both p-and n-type materials were obtained.展开更多
The GaN thick films have been grown on porous GaN template and planar metal-organic chemical vapor deposition(MOCVD)-GaN template by halide vapor phase epitaxy(HVPE). The analysis results indicated that the GaN films ...The GaN thick films have been grown on porous GaN template and planar metal-organic chemical vapor deposition(MOCVD)-GaN template by halide vapor phase epitaxy(HVPE). The analysis results indicated that the GaN films grown on porous and planar GaN templates under the same growth conditions have similar structural, optical, and electrical properties. But the porous GaN templates could significantly reduce the stress in the HVPE-GaN epilayer and enhance the photoluminescence(PL) intensity. The voids in the porous template were critical for the strain relaxation in the GaN films and the increase of the PL intensity. Thus, the porous GaN converted from β-Ga2O3 film as a novel promising template is suitable for the growth of stress-free GaN films.展开更多
In this work, we prepared the β-Ga_2O_3@GaN nanowires(NWs) by oxidizing GaN NWs. High-quality hexagonal wurtzite GaN NWs were achieved and the conversion from GaN to β-Ga_2O_3 was confirmed by x-ray diffraction, Ram...In this work, we prepared the β-Ga_2O_3@GaN nanowires(NWs) by oxidizing GaN NWs. High-quality hexagonal wurtzite GaN NWs were achieved and the conversion from GaN to β-Ga_2O_3 was confirmed by x-ray diffraction, Raman spectroscopy and transmission electron microscopy. The effect of the oxidation temperature and time on the oxidation degree of GaN NWs was investigated systematically. The oxidation rate of GaN NWs was estimated at different temperatures.展开更多
Single-crystal GaN layers have been obtained by nitridingβ-Ga2O3 films in NH3 atmosphere.The effect of the temperature and time on the nitridation and conversion of Ga2O3 films have been investigated.The nitridation ...Single-crystal GaN layers have been obtained by nitridingβ-Ga2O3 films in NH3 atmosphere.The effect of the temperature and time on the nitridation and conversion of Ga2O3 films have been investigated.The nitridation process results in lots of holes in the surface of films.The higher nitridation temperature and longer time can promote the nitridation and improve the crystal quality of GaN films.The converted Ga N porous films show the single-crystal structures and lowstress,which can be used as templates for the epitaxial growth of high-quality GaN.展开更多
Square microdisks with round corners are fabricated using a standard GaN-based blue LED on Si substrates.Whispering gallery-like inodes in the square microdisks are investigated by finite-difference time-domain simula...Square microdisks with round corners are fabricated using a standard GaN-based blue LED on Si substrates.Whispering gallery-like inodes in the square microdisks are investigated by finite-difference time-domain simulation.The simulation results reveal that the round corners in square microdisks can substantially suppress the number of light propagation paths and further reduce the number of optical modes.A con focal microphotoluminescence is performed to analyze the optical properties of the square microdisks at room temperature.The single-mode dominant resonant emission is obtained in the square microdisk with corner radius of 1.5μm.展开更多
A new approach to fabricating high-quality AlInGaN film as a lattice-matched barrier layer in multiple quantum wells(MQWs) is presented. The high-quality AlInGaN film is realized by growing the AlGaN/InGaN short per...A new approach to fabricating high-quality AlInGaN film as a lattice-matched barrier layer in multiple quantum wells(MQWs) is presented. The high-quality AlInGaN film is realized by growing the AlGaN/InGaN short period superlattices through metalorganic chemical vapor deposition, and then being used as a barrier in the MQWs. The crystalline quality of the MQWs with the lattice-matched AlInGaN barrier and that of the conventional InGaN/GaN MQWs are characterized by x-ray diffraction and scanning electron microscopy. The photoluminescence(PL) properties of the InGaN/AlInGa N MQWs are investigated by varying the excitation power density and temperature through comparing with those of the InGaN/GaN MQWs. The integral PL intensity of InGaN/AlInGaN MQWs is over 3 times higher than that of InGaN/GaN MQWs at room temperature under the highest excitation power. Temperature-dependent PL further demonstrates that the internal quantum efficiency of InGaN/AlInGaN MQWs(76.1%) is much higher than that of InGaN/GaN MQWs(21%).The improved luminescence performance of InGaN/AlInGaN MQWs can be attributed to the distinct reduction of the barrier-well lattice mismatch and the strain-induced non-radiative recombination centers.展开更多
基金Supported by the National Key Research and Development Program of China under Grant No 2017YFB0404201the Solid State Lighting and Energy-Saving Electronics Collaborative Innovation Center,PAPDthe State Grid Shandong Electric Power Company
文摘Two-inch Ga_2O_3 films with(ˉ201)-orientation are grown on c-sapphire at 850–1050°C by hydride vapor phase epitaxy. High-resolution x-ray diffraction shows that pure β-Ga_2O_3 with a smooth surface has a higher crystal quality, and the Raman spectra reveal a very small residual strain in β-Ga_2O_3 grown by hydride vapor phase epitaxy compared with bulk single crystal. The optical transmittance is higher than 80% in the visible and near-UV regions, and the optical bandgap energy is calculated to be 4.9 e V.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFB0400100the National Natural Science Foundation of China under Grant Nos 61674076,61674081 and 61605071+4 种基金the Natural Science Foundation of Jiangsu Province under Grant Nos BY2013077,BK20141320 and BE2015111the Six Talent Peaks Project of Jiangsu Province under Grant No XYDXX-081the Open Fund of the State Key Laboratory on Integrated Optoelectronics under Grant No IOSKL2017KF03the Fundamental Research Funds for the Central Universitiesthe Collaborative Innovation Center of Solid State Lighting and Energy-Saving Electronics
文摘GaN-based micro light emitting diodes(micro-LEDs) on silicon(Si)substrates with 40μm in diameter are developed utilizing standard photolithography and inductively coupled plasma etching techniques.From currentvoltage curves,the relatively low turn-on voltage of 2.8 V and low reverse leakage current in the order of 10-8 A/cm2 indicate good electrical characteristics.As the injection current increases,the electroluminescence emission wavelength hardly shifts at around 433 nm, and the relative external quantum efficiency slightly decays,because the impact of quantum-confined Stark effect is not serious in violet-blue micro-LEDs.Since GaN-LEDs are cost effective on large-area Si and suitable for substrate transfer or vertical device structures,the fabricated micro-LEDs on Si should have promising applications in the fields of high-resolution display and optical communication.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFB0403100 and 2017YFB0403101)the National Natural Science Foundation of China(Grant Nos.61704149,61674076,and 61605071)+7 种基金the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BY2013077,BK20141320,and BE2015111)the Project of Science and Technology Development Program in Shandong Province,China(Grant Nos.2013YD02054 and 2013YD02008)the Project of Shandong Provincial Higher Educational Science and Technology Program,China(Grant No.J13LN08)the Collaborative Innovation Center of Solid State Lighting and Energy-saving Electronics,Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the Six-Talent Peaks Project of Jiangsu Province,China(Grant No.XYDXX-081)the Open Fund of the State Key Laboratory on Integrated Optoelectronics,China(Grant No.IOSKL2017KF03)the Project of Autonomous Innovation and Achievement Transformation Program in Zaozhuang City,China(Grant No.2017GH3)the Overseas Study Program Funded by Shandong Provincial Government,China,the Laboratory Open Fund from Jiangsu Key Laboratory of Photoelectric Information Functional Materials,China,and the Doctoral Foundation Project of Zaozhuang University,China.
文摘The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration(~ 1020 cm-3) grown by metal–organic chemical vapor deposition(MOCVD) are systematically studied through optical and electrical properties. Emission lines of shallow oxygen donors and(VⅢ complex)1- as well as VN3+ and neutral Mg acceptors are observed, which indicate that self-compensation is occurred in Mg-doped AlGaN at highly doping levels. The fitting of the temperature-dependent Hall effect data shows that the acceptor activation energy values in Mgdoped AlxGa1-xN(x = 0.23, 0.35) are 172 meV and 242 meV, and the hole concentrations at room temperature are 1.2×1018 cm-3 and 3.3× 1017 cm-3, respectively. Therefore, it is believed that there exists the combined effect of the Coulomb potentials of the dopants and screening of the Coulomb potentials by a high hole concentration. Moreover, due to the high ionized acceptors’ concentration and compensation ratio, the impurity conduction becomes more prominent and the valence band mobility drops sharply at low temperature.
基金the National Natural Science Foundation of China(Grant Nos.62074077,61921005,61974062,and 61974065)the Fundamental Research Funds for the Central Universities,China(Grant No.14380166)+3 种基金Key R&D Program of Jiangsu Province,China(Grant No.BE2020004-3)the National Key R&D Program of China(Grant No.2017YFB0404101)Nature Science Foundation of Jiangsu Province,China(Grant No.BE2015111)Collaborative Innovation Center of Solid State Lighting and Energysaving Electronics.
文摘A systematic investigation on PA-MBE grown GaN with low growth rates(less than 0.2μm/h)has been conducted in a wide growth temperature range,in order to guide future growth of sophisticated fine structures for quantum device applications.Similar to usual growths with higher growth rates,three growth regions have been revealed,namely,Ga droplets,slightly Ga-rich and N-rich 3D growth regions.The slightly Ga-rich region is preferred,in which GaN epilayers demonstrate optimal crystalline quality,which has been demonstrated by streaky RHEED patterns,atomic smooth surface morphology,and very low defect related yellow and blue luminescence bands.The growth temperature is a critical parameter to obtain high quality materials and the optimal growth temperature window(~700-760℃)has been identified.The growth rate shows a strong dependence on growth temperatures in the optimal temperature window,and attention must be paid when growing fine structures at a low growth rate.Mg and Si doped GaN were also studied,and both p-and n-type materials were obtained.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFB0404201)the State Key R&D Program of Jiangsu Province,China(Grant No.BE2019103)+2 种基金the Six-Talent Peaks Project of Jiangsu Province,China(Grant No.XCL-107)the Fund from the Solid-state Lighting and Energy-saving Electronics Collaborative Innovation Center,PAPDthe Fund from the State Grid Shandong Electric Power Company。
文摘The GaN thick films have been grown on porous GaN template and planar metal-organic chemical vapor deposition(MOCVD)-GaN template by halide vapor phase epitaxy(HVPE). The analysis results indicated that the GaN films grown on porous and planar GaN templates under the same growth conditions have similar structural, optical, and electrical properties. But the porous GaN templates could significantly reduce the stress in the HVPE-GaN epilayer and enhance the photoluminescence(PL) intensity. The voids in the porous template were critical for the strain relaxation in the GaN films and the increase of the PL intensity. Thus, the porous GaN converted from β-Ga2O3 film as a novel promising template is suitable for the growth of stress-free GaN films.
基金Project supported by National Key Research and Development Program of China(Grant No.2017YFB0404201)State Key Research and Development Program of Jiangsu Province,China(Grant No.BE2018115)+1 种基金the Fund from the Solid-state Lighting&Energy-saving Electronics Collaborative Innovation Center,PAPDthe Fund from the State Grid Shandong Electric Power Company
文摘In this work, we prepared the β-Ga_2O_3@GaN nanowires(NWs) by oxidizing GaN NWs. High-quality hexagonal wurtzite GaN NWs were achieved and the conversion from GaN to β-Ga_2O_3 was confirmed by x-ray diffraction, Raman spectroscopy and transmission electron microscopy. The effect of the oxidation temperature and time on the oxidation degree of GaN NWs was investigated systematically. The oxidation rate of GaN NWs was estimated at different temperatures.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0404201)the Six-Talent Peaks Project in Jiangsu Province,China(Grant No.XCL-107)+2 种基金the State Key Research and Development Program of Jiangsu Province,China(Grant No.BE2018115)the Fund from the Solid-state Lighting and Energy-saving Electronics Collaborative Innovation Center,PAPDthe Fund from the State Grid Shandong Electric Power Company
文摘Single-crystal GaN layers have been obtained by nitridingβ-Ga2O3 films in NH3 atmosphere.The effect of the temperature and time on the nitridation and conversion of Ga2O3 films have been investigated.The nitridation process results in lots of holes in the surface of films.The higher nitridation temperature and longer time can promote the nitridation and improve the crystal quality of GaN films.The converted Ga N porous films show the single-crystal structures and lowstress,which can be used as templates for the epitaxial growth of high-quality GaN.
基金National Key R&D Program of China under Grant Nos.2016YFB0400102 and 2016YFB0400602National Natural Science Foundation of China under Grant Nos.61674076,61422401,and 51461135002+3 种基金Collaborative Innovation Center of Solid State Lighting and Energy-saving Electronics,Open Fund of the State Key Laboratory on Integrated Optoelectronics under Grant No.IOSKL2017KF03Natural Science Foundation for Young Scientists of Jiangsu Province under Grant No.BK20160376Research Funds from NJU-Yangzhou Institute of Opto-electronics,and the ResearchDevelopment Funds from State Grid Shandong Electric Power Company and Electric Power Research Institute。
文摘Square microdisks with round corners are fabricated using a standard GaN-based blue LED on Si substrates.Whispering gallery-like inodes in the square microdisks are investigated by finite-difference time-domain simulation.The simulation results reveal that the round corners in square microdisks can substantially suppress the number of light propagation paths and further reduce the number of optical modes.A con focal microphotoluminescence is performed to analyze the optical properties of the square microdisks at room temperature.The single-mode dominant resonant emission is obtained in the square microdisk with corner radius of 1.5μm.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274003,61422401,51461135002,and 61334009)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BY2013077,BK20141320,BE2015111,and BK20161324)+1 种基金the Program for New Century Excellent Talents in University,China(Grant No.NCET-11-0229)the Special Semiconductor Materials and Devices Research Funds from State Grid Shandong Electric Power Company,China
文摘A new approach to fabricating high-quality AlInGaN film as a lattice-matched barrier layer in multiple quantum wells(MQWs) is presented. The high-quality AlInGaN film is realized by growing the AlGaN/InGaN short period superlattices through metalorganic chemical vapor deposition, and then being used as a barrier in the MQWs. The crystalline quality of the MQWs with the lattice-matched AlInGaN barrier and that of the conventional InGaN/GaN MQWs are characterized by x-ray diffraction and scanning electron microscopy. The photoluminescence(PL) properties of the InGaN/AlInGa N MQWs are investigated by varying the excitation power density and temperature through comparing with those of the InGaN/GaN MQWs. The integral PL intensity of InGaN/AlInGaN MQWs is over 3 times higher than that of InGaN/GaN MQWs at room temperature under the highest excitation power. Temperature-dependent PL further demonstrates that the internal quantum efficiency of InGaN/AlInGaN MQWs(76.1%) is much higher than that of InGaN/GaN MQWs(21%).The improved luminescence performance of InGaN/AlInGaN MQWs can be attributed to the distinct reduction of the barrier-well lattice mismatch and the strain-induced non-radiative recombination centers.