Nonpolar(11–20) a-plane p-type GaN films were successfully grown on r-plane sapphire substrate with the metal–organic chemical vapor deposition(MOCVD) system. The effects of Mg-doping temperature on the structural a...Nonpolar(11–20) a-plane p-type GaN films were successfully grown on r-plane sapphire substrate with the metal–organic chemical vapor deposition(MOCVD) system. The effects of Mg-doping temperature on the structural and electrical properties of nonpolar p-type GaN films were investigated in detail. It is found that all the surface morphology, crystalline quality, strains, and electrical properties of nonpolar a-plane p-type GaN films are interconnected, and are closely related to the Mg-doping temperature. This means that a proper performance of nonpolar p-type GaN can be expected by optimizing the Mg-doping temperature. In fact, a hole concentration of 1.3×10^(18)cm^(-3), a high Mg activation efficiency of 6.5%,an activation energy of 114 me V for Mg acceptor, and a low anisotropy of 8.3% in crystalline quality were achieved with a growth temperature of 990℃. This approach to optimizing the Mg-doping temperature of the nonpolar a-plane p-type GaN film provides an effective way to fabricate high-efficiency optoelectronic devices in the future.展开更多
In this paper,we use the a-plane InGaN interlayer to improve the property of a-plane GaN.Based on the a-InGaN interlayer,a template exhibits that a regular,porous structure,which acts as a compliant effect,can be obta...In this paper,we use the a-plane InGaN interlayer to improve the property of a-plane GaN.Based on the a-InGaN interlayer,a template exhibits that a regular,porous structure,which acts as a compliant effect,can be obtained to release the strain caused by the lattice and thermal mismatch between a-GaN and r-sapphire.We find that the thickness of InGaN has a great influence on the growth of a-GaN.The surface morphology and crystalline quality both are first improved and then deteriorated with increasing the thickness of the InGaN interlayer.When the InGaN thickness exceeds a critical point,the a-GaN epilayer peels off in the process of cooling down to room temperature.This is an attractive way of lifting off a-GaN films from the sapphire substrate.展开更多
The non-polar a-plane GaN is grown on an r-plane sapphire substrate directly without a buffer layer by metal- organic chemical vapour deposition and the effects of V/III ratio growth conditions are investigated. Atomi...The non-polar a-plane GaN is grown on an r-plane sapphire substrate directly without a buffer layer by metal- organic chemical vapour deposition and the effects of V/III ratio growth conditions are investigated. Atomic force microscopy results show that triangular pits are formed at a relatively high V/III ratio, while a relatively low V/III ratio can enhance the lateral growth rate along the c-axis direction. The higher V/III ratio leads to a high density of pits in comparison with the lower V/III ratio. The surface morphology is improved greatly by using a low V/III ratio of 500 and the roughness mean square of the surface is only 3.9 nm. The high resolution X-ray diffraction characterized crystal structural results show that the rocking curve full width at half maximum along the m axis decreases from 0.757° to 0.720°, while along the c axis increases from 0.220° to 0.251° with the V/III increasing from 500 μmol/min to 2000 μmol/min, which indicates that a relatively low V/III ratio is conducible to the c-axis growth of a-plane GaN.展开更多
The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of ba...The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of basal stacking faults were found to depend heavily upon the V/III ratio. With decreasing V/III ratio, the surface morphology and crystal quality first improved and then deteriorated, and the density of the basal-plane stacking faults also first decreased and then increased. The optimal V/III ratio growth condition for the best surface morphology and crystalline quality and the smallest basal-plane stacking fault density of a-GaN films are found. We also found that the formation of basal-plane stacking faults is an effective way to release strain.展开更多
Nonpolar a-plane GaN epilayers are grown on several r-plane sapphire substrates by metal organic chemical vapour deposition using different nucleation layers： （A） a CaN nucleation layer deposited at low temperature...Nonpolar a-plane GaN epilayers are grown on several r-plane sapphire substrates by metal organic chemical vapour deposition using different nucleation layers： （A） a CaN nucleation layer deposited at low temperature （LT）; （B） an A1N nucleation layer deposited at high temperature; or （C） an LT thin AIN nucleation layer with an AIN layer and an A1N/A1CaN superlattice both subsequently deposited at high temperature. The samples have been characterized by Xray diffraction （XRD）, atomic force microscopy and photoluminescence. The GaN layers grown using nucleation layers B and C show narrower XRD rocking curves than that using nucleation layer A, indicating a reduction in crystal defect density. Furthermore, the GaN layer grown using nucleation layer C exhibits a surface morphology with triangular defect pits eliminated completely. The improved optical property, corresponding to the enhanced crystal quality, is also confirmed by temperature-dependent and excitation power-dependent photoluminescence measurements.展开更多
Hydride vapor phase epitaxy （HVPE） is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy （MOVPE）. The surface morphology and microstructures of...Hydride vapor phase epitaxy （HVPE） is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy （MOVPE）. The surface morphology and microstructures of the samples are characterized by atomic force microscopy. The full width at half maximum （FWHM） of the HVPE sample shows a W-shape and that of the MOVPE sample shows an M-shape plane with the degree of 0 in the high-resolution x-ray diffraction （HRXRD） results. The surface morphology attributes to this significant anisotropic. HRXRD reveals that there is a significant reduction in the FWHM, both on-axis and off-axis for HVPE GaN are compared with the MOVPE template. The decrease of the FWHM of E2 （high） Raman scat tering spectra further indicates the improvement of crystal quality after HVPE. By comparing the results of secondary- ion-mass spectroscope and photoluminescence spectrum of the samples grown by HVPE and MOVPE, we propose that C-involved defects are originally responsible for the yellow luminescence.展开更多
Effects of the growth temperature on morphological and microstructural evolution of a-plane GaN films grown on r-plane sapphires by metal organic chemical vapor deposition are investigated by atomic force microscopy a...Effects of the growth temperature on morphological and microstructural evolution of a-plane GaN films grown on r-plane sapphires by metal organic chemical vapor deposition are investigated by atomic force microscopy and secondary ion mass spectroscopy （SIMS）. Surface morphology, structural quality and related impurity incorpora- tion are very sensitive to the growth temperature. A significant difference of yellow luminescence is observed and attributed to the incorporation of carbon into GaN films, which is confirmed by SIMS analysis. Our results show that the sample with triangular-pit morphology has sample with pentagon-like pit morphology, which is significantly higher concentrations of oxygen than the other induced by the existence of an N-face in triangular pits.展开更多
Nonpolar a-plane [110] GaN has been grown on r-plane [1■02] sapphire by MOCVD, and investigated by high resolution X-ray diffraction and atomic force microscopy. As opposed to the c-direction, this particular orienta...Nonpolar a-plane [110] GaN has been grown on r-plane [1■02] sapphire by MOCVD, and investigated by high resolution X-ray diffraction and atomic force microscopy. As opposed to the c-direction, this particular orientation is non-polar, and it avoids polarization charge, the associated screening charge and the consequent band bending. Both low-temperature GaN buffer and high-temperature AlN buffer are used for a-plane GaN growth on r-plane sapphire, and the triangular pits and pleat morphology come forth with different buffers, the possible reasons for which are discussed. The triangular and pleat direction are also investigated. A novel modulate buffer is used for a-plane GaN growth on r-plane sapphire, and with this technique, the crystal quality has been greatly improved.展开更多
基金Project supported by the National Key Research and Development Program of China (Grant Nos.2021YFB3601000 and 2021YFB3601002)the National Natural Science Foundation of China (Grant Nos.62074077,61921005,61974062,62204121,and 61904082)+1 种基金Leading-edge Technology Program of Jiangsu Natural Science Foundation (Grant No.BE2021008-2)the China Postdoctoral Science Foundation (Grant No.2020M671441)。
文摘Nonpolar(11–20) a-plane p-type GaN films were successfully grown on r-plane sapphire substrate with the metal–organic chemical vapor deposition(MOCVD) system. The effects of Mg-doping temperature on the structural and electrical properties of nonpolar p-type GaN films were investigated in detail. It is found that all the surface morphology, crystalline quality, strains, and electrical properties of nonpolar a-plane p-type GaN films are interconnected, and are closely related to the Mg-doping temperature. This means that a proper performance of nonpolar p-type GaN can be expected by optimizing the Mg-doping temperature. In fact, a hole concentration of 1.3×10^(18)cm^(-3), a high Mg activation efficiency of 6.5%,an activation energy of 114 me V for Mg acceptor, and a low anisotropy of 8.3% in crystalline quality were achieved with a growth temperature of 990℃. This approach to optimizing the Mg-doping temperature of the nonpolar a-plane p-type GaN film provides an effective way to fabricate high-efficiency optoelectronic devices in the future.
基金supported by the National Natural Science Foundation of China(Grant Nos.91233111,61274041,and 11275228)the Special Funds for Major State Basic Research Project of China(Grant No.2012CB619305)+1 种基金the National High Technology R&D Program of China(Grant Nos.2014AA032603 and2014AA032609)the Guangdong Provincial Special Fund for LED Industrial Development,China(Grant No.2012A080302003)
文摘In this paper,we use the a-plane InGaN interlayer to improve the property of a-plane GaN.Based on the a-InGaN interlayer,a template exhibits that a regular,porous structure,which acts as a compliant effect,can be obtained to release the strain caused by the lattice and thermal mismatch between a-GaN and r-sapphire.We find that the thickness of InGaN has a great influence on the growth of a-GaN.The surface morphology and crystalline quality both are first improved and then deteriorated with increasing the thickness of the InGaN interlayer.When the InGaN thickness exceeds a critical point,the a-GaN epilayer peels off in the process of cooling down to room temperature.This is an attractive way of lifting off a-GaN films from the sapphire substrate.
基金supported by the Special Funds for Major State Basic Research Project of China (Grant No. 2011CB301900)High Technology Research Program of 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 Natural Science Foundation of Jiangsu Province of China (Grant Nos. BK2008019, BK2010385, BK2009255, and BK2010178)the Research Funds from NJU-Yangzhou Institute of Opto-electronics, China
文摘The non-polar a-plane GaN is grown on an r-plane sapphire substrate directly without a buffer layer by metal- organic chemical vapour deposition and the effects of V/III ratio growth conditions are investigated. Atomic force microscopy results show that triangular pits are formed at a relatively high V/III ratio, while a relatively low V/III ratio can enhance the lateral growth rate along the c-axis direction. The higher V/III ratio leads to a high density of pits in comparison with the lower V/III ratio. The surface morphology is improved greatly by using a low V/III ratio of 500 and the roughness mean square of the surface is only 3.9 nm. The high resolution X-ray diffraction characterized crystal structural results show that the rocking curve full width at half maximum along the m axis decreases from 0.757° to 0.720°, while along the c axis increases from 0.220° to 0.251° with the V/III increasing from 500 μmol/min to 2000 μmol/min, which indicates that a relatively low V/III ratio is conducible to the c-axis growth of a-plane GaN.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.91233111,61274041,11275228,61006004,and 61076001)the Special Funds for Major State Basic Research Project (973 Program) of China (Grant No.2012CB619305)+1 种基金the 863 High Technology R&D Program of China (Grant No.2011AA03A101)the Special Fund for LED Industrial Development of Guangdong Province of China (Grant No.2012A080302003)
文摘The effects of V/Ill growth flux ratio on a-plane GaN films grown on r-plane sapphire substrates with an InGaN interlayer are investigated. The surface morphology, crystalline quality, strain states, and density of basal stacking faults were found to depend heavily upon the V/III ratio. With decreasing V/III ratio, the surface morphology and crystal quality first improved and then deteriorated, and the density of the basal-plane stacking faults also first decreased and then increased. The optimal V/III ratio growth condition for the best surface morphology and crystalline quality and the smallest basal-plane stacking fault density of a-GaN films are found. We also found that the formation of basal-plane stacking faults is an effective way to release strain.
基金Project supported by the National Key Science & Technology Major Project of the Ministry of Science and Technology of China(Grant No. 2008ZX01002-002)the Major Program and the Key Program of the National Natural Science Foundation of China(Grant Nos. 60890191 and 60736033)
文摘Nonpolar a-plane GaN epilayers are grown on several r-plane sapphire substrates by metal organic chemical vapour deposition using different nucleation layers： （A） a CaN nucleation layer deposited at low temperature （LT）; （B） an A1N nucleation layer deposited at high temperature; or （C） an LT thin AIN nucleation layer with an AIN layer and an A1N/A1CaN superlattice both subsequently deposited at high temperature. The samples have been characterized by Xray diffraction （XRD）, atomic force microscopy and photoluminescence. The GaN layers grown using nucleation layers B and C show narrower XRD rocking curves than that using nucleation layer A, indicating a reduction in crystal defect density. Furthermore, the GaN layer grown using nucleation layer C exhibits a surface morphology with triangular defect pits eliminated completely. The improved optical property, corresponding to the enhanced crystal quality, is also confirmed by temperature-dependent and excitation power-dependent photoluminescence measurements.
基金Supported by the National Natural Science Foundation of China under Grant No 61204006the Fundamental Research Funds for the Central Universities under Grant No 7214570101the National Key Science and Technology Special Project under Grant No 2008ZX01002-002
文摘Hydride vapor phase epitaxy （HVPE） is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy （MOVPE）. The surface morphology and microstructures of the samples are characterized by atomic force microscopy. The full width at half maximum （FWHM） of the HVPE sample shows a W-shape and that of the MOVPE sample shows an M-shape plane with the degree of 0 in the high-resolution x-ray diffraction （HRXRD） results. The surface morphology attributes to this significant anisotropic. HRXRD reveals that there is a significant reduction in the FWHM, both on-axis and off-axis for HVPE GaN are compared with the MOVPE template. The decrease of the FWHM of E2 （high） Raman scat tering spectra further indicates the improvement of crystal quality after HVPE. By comparing the results of secondary- ion-mass spectroscope and photoluminescence spectrum of the samples grown by HVPE and MOVPE, we propose that C-involved defects are originally responsible for the yellow luminescence.
基金Supported by the National Natural Science Foundation of China under Grant No 61204006the Fundamental Research Funds for the Central Universities under Grant No K50511250002
文摘Effects of the growth temperature on morphological and microstructural evolution of a-plane GaN films grown on r-plane sapphires by metal organic chemical vapor deposition are investigated by atomic force microscopy and secondary ion mass spectroscopy （SIMS）. Surface morphology, structural quality and related impurity incorpora- tion are very sensitive to the growth temperature. A significant difference of yellow luminescence is observed and attributed to the incorporation of carbon into GaN films, which is confirmed by SIMS analysis. Our results show that the sample with triangular-pit morphology has sample with pentagon-like pit morphology, which is significantly higher concentrations of oxygen than the other induced by the existence of an N-face in triangular pits.
基金supported by the National Natural Science Foundation of China (No. 60736033)the State Key Development Program for Basic Research of China (No. 513270407)
文摘Nonpolar a-plane [110] GaN has been grown on r-plane [1■02] sapphire by MOCVD, and investigated by high resolution X-ray diffraction and atomic force microscopy. As opposed to the c-direction, this particular orientation is non-polar, and it avoids polarization charge, the associated screening charge and the consequent band bending. Both low-temperature GaN buffer and high-temperature AlN buffer are used for a-plane GaN growth on r-plane sapphire, and the triangular pits and pleat morphology come forth with different buffers, the possible reasons for which are discussed. The triangular and pleat direction are also investigated. A novel modulate buffer is used for a-plane GaN growth on r-plane sapphire, and with this technique, the crystal quality has been greatly improved.
