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
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
GaN nanorods are fabricated using inductively coupled plasma etching with Ni nano-island masks. The poly [2- methoxy-5-（2-ethyl）hexoxy-l,4-phenylenevinylene] （MEH-PPV）/GaN-nanorod hybrid structure is fabricated by...GaN nanorods are fabricated using inductively coupled plasma etching with Ni nano-island masks. The poly [2- methoxy-5-（2-ethyl）hexoxy-l,4-phenylenevinylene] （MEH-PPV）/GaN-nanorod hybrid structure is fabricated by depositing the MEH-PPV film on the GaN nanorods by using the spin-coating process. In the hybrid structure, the spatial separation is minimized to achieve high-emciency non-radiative resonant energy transfer. Optical properties of a novel device consisting of MEH-PPV/GaN-nanorod hybrid structure is studied by analyzing photoluminescenee （PL） spectra. Compared with the pure GaN nanorods, the PL intensity of the band edge emission of GaN in the MEH-PPV/GaN-nanorods is enhanced as much as three times, and the intensity of the yellow band is suppressed slightly. The obtained results are analyzed by energy transfer between the GaN nanorods and the MEH-PPV. An energy transfer model is proposed to explain the phenomenon.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
A series of experiments were conducted to systematically study the effects of etching conditions on GaN by a con-venient photo-assisted chemical （PAC） etching method. The solution concentration has an evident influe...A series of experiments were conducted to systematically study the effects of etching conditions on GaN by a con-venient photo-assisted chemical （PAC） etching method. The solution concentration has an evident influence on the surface morphology of GaN and the optimal solution concentrations for GaN hexagonal pyramids have been identified. GaN with hexagonal pyramids have higher crystal quality and tensile strain relaxation compared with as-grown GaN. A detailed anal- ysis about evolution of the size, density and optical property of GaN hexagonal pyramids is described as a function of light intensity. The intensity of photoluminescence spectra of GaN etched with hexagonal pyramids significantly increases compared to that of as-grown GaN due to multiple scattering events, high quality GaN with pyramids and the Bragg effect.展开更多
To understand the mechanism of Gallium nitride （GaN） film growth is of great importance for their potential applications. In this paper, we investigate the growth behavior of the GaN film by combining computational ...To understand the mechanism of Gallium nitride （GaN） film growth is of great importance for their potential applications. In this paper, we investigate the growth behavior of the GaN film by combining computational fluid dynamics （CFD） and molecular dynamics （MD） simulations. Both of the simulations show that V/III mixture degree can have important impacts on the deposition behavior, and it is found that the more uniform the mixture is, the better the growth is. Besides, by using MD simulations, we illustrate the whole process of the GaN growth. Furthermore, we also find that the V/III ratio can affect the final roughness of the GaN film. When the V/III ratio is high, the surface of final GaN film is smooth. The present study provides insights into GaN growth from the macroscopic and microscopic views, which may provide some suggestions on better experimental GaN preparation.展开更多
Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system. Three quantum wells with blue-light-emitting, green-light-emitt...Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system. Three quantum wells with blue-light-emitting, green-light-emitting and red-light-emitting structures were grown according to the design. The surface morphology of the film was observed by using atomic force microscopy. The films were characterized by their photoluminescence measurements. X-ray diffraction t9/2/9 scan spectroscopy was carried out on the multi-quantum wells. The secondary fringes of the symmetric ω/2θ X-ray diffraction scan peaks indicate that the thicknesses and the alloy compositions of the individual quantum wells are repeatable throughout the active region. The room temperature photoluminescence spectra of the structures indicate that the white light emission of the multi-quantum wells is obtained. The light spectrum covers 400 700 nm, which is almost the whole visible light spectrum.展开更多
We report on the photoluminescent characteristics of InGaN/GaN multiple quantum well(MQW)nanorod arrays with high internal quantum efficiency.The InGaN/GaN MQWs are grown by metalorganic chemical vapor deposition on c...We report on the photoluminescent characteristics of InGaN/GaN multiple quantum well(MQW)nanorod arrays with high internal quantum efficiency.The InGaN/GaN MQWs are grown by metalorganic chemical vapor deposition on c-plane sapphire substrates,and then the MQW nanorod arrays are fabricated by using inductively coupled plasma etching with self-assembled Ni nanoparticle mask with low-damage etching technique.The typical diameter of the nanorods is from 200 nm to 300 nm and the length is around 800 nm,which almost is dislocation free.At room temperature,an enhancement of 3.1 times in total integrated photoluminescence intensity is achieved from the MQW nanorod arrays,in comparison to that of the as-grown MQW structure.Based on the temperature-dependent photoluminescence measurements,the internal quantum efficiency of the nanorod structure is 59.2%,i.e.,1.75 times of as-grown MQW structure(33.8%).Therefore,the nanorod structure with a significant reduction of defects can be a very promising candidate for highly efficient light emitting devices.展开更多
GaN with hexagonal pyramids is fabricated using the photo-assisted electroless chemical etching method.Defective areas of the GaN substrate are selectively etched in a mixed solution of KOH and K2S2O8 under ultraviole...GaN with hexagonal pyramids is fabricated using the photo-assisted electroless chemical etching method.Defective areas of the GaN substrate are selectively etched in a mixed solution of KOH and K2S2O8 under ultraviolet illumination,producing submicron-sized pyramids.Hexagonal pyramids on the etched GaN with well-defined{1011}facets and very sharp tips are formed.High-resolution x-ray diffraction shows that etched GaN with pyramids has a higher crystal quality,and micro-Raman spectra reveal a tensile stress relaxation in GaN with pyramids compared with normal GaN.The cathodoluminescence intensity of GaN after etching is significantly increased by three times,which is attributed to the reduction in the internal reflection,high-quality GaN with pyramids and the Bragg effect.展开更多
The influence of dry etching damage on the internal quantum efficiency of InGaN/GaN nanorod multiple quantum wells (MQWs) is studied.The samples were etched by inductively coupled plasma (ICP) etching via a selfassemb...The influence of dry etching damage on the internal quantum efficiency of InGaN/GaN nanorod multiple quantum wells (MQWs) is studied.The samples were etched by inductively coupled plasma (ICP) etching via a selfassembled nickel nanomask,and examined by room-temperature photoluminescence measurement.The key parameters in the etching process are rf power and ICP power.The internal quantum efficiency of nanorod MQWs shows a 5.6 times decrease substantially with the rf power increasing from 3W to 100W.However,it is slightly influenced by the ICP power,which shows 30% variation over a wide ICP power range between 30W and 600W.Under the optimized etching condition,the internal quantum efficiency of nanorod MQWs can be 40% that of the as-grown MQW sample,and the external quantum efficiency of nanorod MQWs can be about 4 times that of the as-grown one.展开更多
Roughened surfaces of light-emitting diodes(LEDs)provide substantial improvement in light extraction efficiency.By preparing the self-assemble nanoporous Ni template through rapid annealing of a thin Ni film,followed ...Roughened surfaces of light-emitting diodes(LEDs)provide substantial improvement in light extraction efficiency.By preparing the self-assemble nanoporous Ni template through rapid annealing of a thin Ni film,followed by a low damage dry etching process,a p-side-up LED with a roughened surface has been fabricated.Compared to a conventional LED with plane surface,the light output of LEDs with nanoporous p-GaN surface increases up to 71%and 36%at applied currents of 1 mA and 20 mA,respectively.Meanwhile,the electrical characteristics are not degraded obviously after surface roughening.展开更多
Blue-red complex light emitting InGaN/GaN multi-quantum well(MQW)structures are fabricated by metal organic chemical vapor deposition(MOCVD).The structures are grown on a 2-inch diameter(0001)oriented(c−face)sapphire ...Blue-red complex light emitting InGaN/GaN multi-quantum well(MQW)structures are fabricated by metal organic chemical vapor deposition(MOCVD).The structures are grown on a 2-inch diameter(0001)oriented(c−face)sapphire substrate,which consists of an approximately 2-µm−thick GaN template and a five-period layer consisting of a 4.9-nm-thick In0.18Ga0.82N well layer and a GaN barrier layer.The surface morphology of the MQW structures is observed by an atomic force microscope(AFM),which indicates the presence of islands of several tens of nanometers in height on the surface.The high resolution x−ray diffraction(XRD)θ/2θscan is carried out on the symmetric(0002)of the InGaN/GaN MQW structures.At least four order satellite peaks presented in the XRD spectrum indicate that the thickness and alloy compositions of the individual quantum wells are repeatable throughout the active region.Besides the 364 nm GaN band edge emission,two main emissions of blue and amber light from these MQWs are found,which possibly originate from the carrier recombinations in the InGaN/GaN QWs and InGaN quasi-quantum dots embedded in the QWs.展开更多
基金supported by special funds for major state basic research project(2011CB301900)hi-tech research project (2009AA03A198)+2 种基金national nature science foundation of China(60990311,60721063,60906025,60936004)The nature science foundation of Jiangsu province(BK2008019,BK2009255,BK2010178)the researchfunds from NJU-Yangzhou Institute of Opto-electronics
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Supported by the National Key Technology Research and Development Program under Grant No 2016YFB0400100the National Basic Research Program of China under Grant No 2012CB619304+4 种基金the High-Technology Research and Development Program of China under Grant Nos 2014AA032605 and 2015AA033305the National Natural Science Foundation of China under Grant Nos61274003,61422401,51461135002 and 61334009the Key Technology Research of Jiangsu Province under Grant No BE2015111the Solid State Lighting and Energy-Saving Electronics Collaborative Innovation Centerthe Research Funds from NJU-Yangzhou Institute of Opto-electronics
文摘GaN nanorods are fabricated using inductively coupled plasma etching with Ni nano-island masks. The poly [2- methoxy-5-（2-ethyl）hexoxy-l,4-phenylenevinylene] （MEH-PPV）/GaN-nanorod hybrid structure is fabricated by depositing the MEH-PPV film on the GaN nanorods by using the spin-coating process. In the hybrid structure, the spatial separation is minimized to achieve high-emciency non-radiative resonant energy transfer. Optical properties of a novel device consisting of MEH-PPV/GaN-nanorod hybrid structure is studied by analyzing photoluminescenee （PL） spectra. Compared with the pure GaN nanorods, the PL intensity of the band edge emission of GaN in the MEH-PPV/GaN-nanorods is enhanced as much as three times, and the intensity of the yellow band is suppressed slightly. The obtained results are analyzed by energy transfer between the GaN nanorods and the MEH-PPV. An energy transfer model is proposed to explain the phenomenon.
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.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB301900,2012CB619304,and 2010CB327504)the National High Technology Research and Development Program of China(Grant No.2011AA03A103)+1 种基金the National Nature Science Foundation of China(Grant Nos.60990311,60906025,60936004,and 61176063)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK2011010 and BK2009255)
文摘A series of experiments were conducted to systematically study the effects of etching conditions on GaN by a con-venient photo-assisted chemical （PAC） etching method. The solution concentration has an evident influence on the surface morphology of GaN and the optimal solution concentrations for GaN hexagonal pyramids have been identified. GaN with hexagonal pyramids have higher crystal quality and tensile strain relaxation compared with as-grown GaN. A detailed anal- ysis about evolution of the size, density and optical property of GaN hexagonal pyramids is described as a function of light intensity. The intensity of photoluminescence spectra of GaN etched with hexagonal pyramids significantly increases compared to that of as-grown GaN due to multiple scattering events, high quality GaN with pyramids and the Bragg effect.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB301900)the National High Technology Research and DevelopmentProgram of China (Grant No. 2011AA03A103)+1 种基金the National Natural Science Foundation of China (Grant Nos. 60990311, 60820106003, 60906025, and60936004)the Natural Science Foundation of Jiangsu Province, China (Grant Nos. BK2011010, BK2010385, BK2009255, and BK2010178)
文摘To understand the mechanism of Gallium nitride （GaN） film growth is of great importance for their potential applications. In this paper, we investigate the growth behavior of the GaN film by combining computational fluid dynamics （CFD） and molecular dynamics （MD） simulations. Both of the simulations show that V/III mixture degree can have important impacts on the deposition behavior, and it is found that the more uniform the mixture is, the better the growth is. Besides, by using MD simulations, we illustrate the whole process of the GaN growth. Furthermore, we also find that the V/III ratio can affect the final roughness of the GaN film. When the V/III ratio is high, the surface of final GaN film is smooth. The present study provides insights into GaN growth from the macroscopic and microscopic views, which may provide some suggestions on better experimental GaN preparation.
基金supported by the Special Funds for Major State Basic Research Project,China(Grant No.2011CB301900)the Hi-tech Research Project,China(Grant No.2009AA03A198)+2 种基金the National Natural Science Foundation of China(Grant Nos.60990311, 60721063,60906025,60936004,60731160628,and 60820106003)the Nature Science Foundation of Jiangsu Province,China (Grant Nos.BK2008019,BK2010385,BK2009255,and BK2010178)the Research Funds from NJU-Yangzhou Institute of Opto-electronics,China
文摘Wide spectral white light emitting diodes have been designed and grown on a sapphire substrate by using a metal-organic chemical vapor deposition system. Three quantum wells with blue-light-emitting, green-light-emitting and red-light-emitting structures were grown according to the design. The surface morphology of the film was observed by using atomic force microscopy. The films were characterized by their photoluminescence measurements. X-ray diffraction t9/2/9 scan spectroscopy was carried out on the multi-quantum wells. The secondary fringes of the symmetric ω/2θ X-ray diffraction scan peaks indicate that the thicknesses and the alloy compositions of the individual quantum wells are repeatable throughout the active region. The room temperature photoluminescence spectra of the structures indicate that the white light emission of the multi-quantum wells is obtained. The light spectrum covers 400 700 nm, which is almost the whole visible light spectrum.
基金Supported by the National Basic Research Program of China under Grant No 2011CB301900the National Natural Science Foundation of China under Grant Nos 61176063,60990311,60820106003,60906025,and 60936004+1 种基金the Natural Science Foundation of Jiangsu Province under Grant Nos BK2008019,BK2010385,BK2009255,and BK2010178the Research Funds from NJUYangzhou Institute of Optoelectronics.
文摘We report on the photoluminescent characteristics of InGaN/GaN multiple quantum well(MQW)nanorod arrays with high internal quantum efficiency.The InGaN/GaN MQWs are grown by metalorganic chemical vapor deposition on c-plane sapphire substrates,and then the MQW nanorod arrays are fabricated by using inductively coupled plasma etching with self-assembled Ni nanoparticle mask with low-damage etching technique.The typical diameter of the nanorods is from 200 nm to 300 nm and the length is around 800 nm,which almost is dislocation free.At room temperature,an enhancement of 3.1 times in total integrated photoluminescence intensity is achieved from the MQW nanorod arrays,in comparison to that of the as-grown MQW structure.Based on the temperature-dependent photoluminescence measurements,the internal quantum efficiency of the nanorod structure is 59.2%,i.e.,1.75 times of as-grown MQW structure(33.8%).Therefore,the nanorod structure with a significant reduction of defects can be a very promising candidate for highly efficient light emitting devices.
基金the National Basic Research Program of China under Grant Nos 2011CB301900,2012CB619304 and 2010CB327504the High-Technology Research and Development Program of China under Grant No 2011AA03A103+1 种基金the National Natural Science Foundation of China under Grant Nos 60990311,60906025,60936004 and 61176063the Natural Science Foundation of Jiangsu Province under Grant Nos BK2011010 and BK2009255.
文摘GaN with hexagonal pyramids is fabricated using the photo-assisted electroless chemical etching method.Defective areas of the GaN substrate are selectively etched in a mixed solution of KOH and K2S2O8 under ultraviolet illumination,producing submicron-sized pyramids.Hexagonal pyramids on the etched GaN with well-defined{1011}facets and very sharp tips are formed.High-resolution x-ray diffraction shows that etched GaN with pyramids has a higher crystal quality,and micro-Raman spectra reveal a tensile stress relaxation in GaN with pyramids compared with normal GaN.The cathodoluminescence intensity of GaN after etching is significantly increased by three times,which is attributed to the reduction in the internal reflection,high-quality GaN with pyramids and the Bragg effect.
基金Supported by the National Basic Research Program of China under Grant No 2011CB301900the National Natural Science Foundation of China(61176063,60990311,60820106003,60906025,60936004)+1 种基金The Natural Science Foundation of Jiangsu Province(BK2008019,BK2010385,BK2009255,BK2010178)the Research Funds from NJU-Yangzhou Institute of Optoelectronics.
文摘The influence of dry etching damage on the internal quantum efficiency of InGaN/GaN nanorod multiple quantum wells (MQWs) is studied.The samples were etched by inductively coupled plasma (ICP) etching via a selfassembled nickel nanomask,and examined by room-temperature photoluminescence measurement.The key parameters in the etching process are rf power and ICP power.The internal quantum efficiency of nanorod MQWs shows a 5.6 times decrease substantially with the rf power increasing from 3W to 100W.However,it is slightly influenced by the ICP power,which shows 30% variation over a wide ICP power range between 30W and 600W.Under the optimized etching condition,the internal quantum efficiency of nanorod MQWs can be 40% that of the as-grown MQW sample,and the external quantum efficiency of nanorod MQWs can be about 4 times that of the as-grown one.
基金Supported by the National Basic Research Program of China(2011CB301900)the National Natural Science Foundation of China(61176063,60990311,60820106003,60906025,60936004)+1 种基金The Nature Science Foundation of Jiangsu Province(BK2008019,BK2010385,BK2009255,BK2010178)the Research Funds from NJU-Yangzhou Institute of Optoelectronics.
文摘Roughened surfaces of light-emitting diodes(LEDs)provide substantial improvement in light extraction efficiency.By preparing the self-assemble nanoporous Ni template through rapid annealing of a thin Ni film,followed by a low damage dry etching process,a p-side-up LED with a roughened surface has been fabricated.Compared to a conventional LED with plane surface,the light output of LEDs with nanoporous p-GaN surface increases up to 71%and 36%at applied currents of 1 mA and 20 mA,respectively.Meanwhile,the electrical characteristics are not degraded obviously after surface roughening.
基金by the National Basic Research Program of China under Grant No 2011CB301900the National High-Technology Research and Development Program of China under Grant No 2009AA03A198+2 种基金the National Natural Science Foundation of China under Grant Nos 60721063,60676057,60731160628,60820106003,60990311 and 60906025the Natural Science Foundation of Jiangsu Province(BK2008019,BK2009255)the Research Funds from NJU-Yangzhou Institute of Opto-electronics.
文摘Blue-red complex light emitting InGaN/GaN multi-quantum well(MQW)structures are fabricated by metal organic chemical vapor deposition(MOCVD).The structures are grown on a 2-inch diameter(0001)oriented(c−face)sapphire substrate,which consists of an approximately 2-µm−thick GaN template and a five-period layer consisting of a 4.9-nm-thick In0.18Ga0.82N well layer and a GaN barrier layer.The surface morphology of the MQW structures is observed by an atomic force microscope(AFM),which indicates the presence of islands of several tens of nanometers in height on the surface.The high resolution x−ray diffraction(XRD)θ/2θscan is carried out on the symmetric(0002)of the InGaN/GaN MQW structures.At least four order satellite peaks presented in the XRD spectrum indicate that the thickness and alloy compositions of the individual quantum wells are repeatable throughout the active region.Besides the 364 nm GaN band edge emission,two main emissions of blue and amber light from these MQWs are found,which possibly originate from the carrier recombinations in the InGaN/GaN QWs and InGaN quasi-quantum dots embedded in the QWs.
