采用MOCVD(metal organic chemical vapor deposition)生长方法,对比在AlN层上加入δAl/AlN缓冲层和不加入δAl/AlN缓冲层两种生长结构,在Si(111)衬底上生长GaN.实验结果表明,在加入δAl/AlN缓冲层后,GaN外延层的裂纹密度得到了有效的降...采用MOCVD(metal organic chemical vapor deposition)生长方法,对比在AlN层上加入δAl/AlN缓冲层和不加入δAl/AlN缓冲层两种生长结构,在Si(111)衬底上生长GaN.实验结果表明,在加入δAl/AlN缓冲层后,GaN外延层的裂纹密度得到了有效的降低,晶体质量也得到了明显的提高.通过MOCVD生长方法,利用光学显微镜、XRD和Raman等分析测试手段,研究了δAl/AlN缓冲层对GaN外延层的影响,获得了裂纹密度小、晶体质量高的GaN材料.展开更多
AlN/GaN superlattice buffer is inserted between GaN epitaxiai layer and Si substrate before epitaxiai growth of GaN layer. High-quality and crack-free GaN epitaxiai layers can be obtained by inserting AlN/GaN superlat...AlN/GaN superlattice buffer is inserted between GaN epitaxiai layer and Si substrate before epitaxiai growth of GaN layer. High-quality and crack-free GaN epitaxiai layers can be obtained by inserting AlN/GaN superlattice buffer layer. The influence of AlN/GaN superlattice buffer layer on the properties of GaN films are investigated in this paper. One of the important roles of the superlattice is to release tensile strain between Si substrate and epilayer. Raman spectra show a substantial decrease of in-plane tensile strain in GaN layers by using AlN/GaN superlattice buffer layer. Moreover, TEM cross-sectional images show that the densities of both screw and edge dislocations are significantly reduced. The GaN films grown on Si with the superlattice buffer also have better surface morphology and optical properties.展开更多
Electrical properties of Aly Ga1-yN/Alx Ga1-x N/AlN//GaN structure are investigated by solving coupled Schrodinger and Poisson equation self-consistently. Our calculations show that the two-dimensional electron gas （...Electrical properties of Aly Ga1-yN/Alx Ga1-x N/AlN//GaN structure are investigated by solving coupled Schrodinger and Poisson equation self-consistently. Our calculations show that the two-dimensional electron gas （2DEG） density will decrease with the thickness of the second barrier （Aly Ga1-y N） once the AlN content of the second barrier is smaller than a critical value yc, and will increase with the thickness of the second barrier （AlyGal_yN） when the critical AlN content of the second barrier yc is exceeded. Our calculations also show that the critical AIN content of the second barrier yc will increase with the AIN content and the thickness of the first barrier layer （AlxGa1-xN）.展开更多
The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is...The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature.The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template.The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects.The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.展开更多
Mg-doped AlGaN and GaN/AlGaN superlattices are grown by metalorganic chemical vapour deposition （MOCVD） Rapid thermal annealing （RTA） treatments are carried out on the samples. Hall and high resolution x-ray diffr...Mg-doped AlGaN and GaN/AlGaN superlattices are grown by metalorganic chemical vapour deposition （MOCVD） Rapid thermal annealing （RTA） treatments are carried out on the samples. Hall and high resolution x-ray diffraction measurements are used to characterize the electrical and structural prosperities of the as-grown and annealed samples, respectively. The results of hall measurements show that after annealing, the Mg-doped AIGaN sample can not obtain the distinct hole concentration and can acquire a resistivity of 1.4 ×10^3 Ωcm. However, with the same annealing treatment, the GaN/AlGaN superlattice sample has a hole concentration of 1.7 × 10^17 cm-3 and a resistivity of 5.6Ωcm. The piezoelectric field in the GaN/AlGaN superlattices improves the activation efficiency of Mg acceptors, which leads to higher hole concentration and lower p-type resistivity.展开更多
文摘采用MOCVD(metal organic chemical vapor deposition)生长方法,对比在AlN层上加入δAl/AlN缓冲层和不加入δAl/AlN缓冲层两种生长结构,在Si(111)衬底上生长GaN.实验结果表明,在加入δAl/AlN缓冲层后,GaN外延层的裂纹密度得到了有效的降低,晶体质量也得到了明显的提高.通过MOCVD生长方法,利用光学显微镜、XRD和Raman等分析测试手段,研究了δAl/AlN缓冲层对GaN外延层的影响,获得了裂纹密度小、晶体质量高的GaN材料.
文摘AlN/GaN superlattice buffer is inserted between GaN epitaxiai layer and Si substrate before epitaxiai growth of GaN layer. High-quality and crack-free GaN epitaxiai layers can be obtained by inserting AlN/GaN superlattice buffer layer. The influence of AlN/GaN superlattice buffer layer on the properties of GaN films are investigated in this paper. One of the important roles of the superlattice is to release tensile strain between Si substrate and epilayer. Raman spectra show a substantial decrease of in-plane tensile strain in GaN layers by using AlN/GaN superlattice buffer layer. Moreover, TEM cross-sectional images show that the densities of both screw and edge dislocations are significantly reduced. The GaN films grown on Si with the superlattice buffer also have better surface morphology and optical properties.
文摘Electrical properties of Aly Ga1-yN/Alx Ga1-x N/AlN//GaN structure are investigated by solving coupled Schrodinger and Poisson equation self-consistently. Our calculations show that the two-dimensional electron gas （2DEG） density will decrease with the thickness of the second barrier （Aly Ga1-y N） once the AlN content of the second barrier is smaller than a critical value yc, and will increase with the thickness of the second barrier （AlyGal_yN） when the critical AlN content of the second barrier yc is exceeded. Our calculations also show that the critical AIN content of the second barrier yc will increase with the AIN content and the thickness of the first barrier layer （AlxGa1-xN）.
基金Project supported by Special Funds for Major State Basic Research Project(G2000683 and 2002CB311903)Nationel Natural Foundation of China(60136020)Key Imnovation Program of Chinese Academy of Science and National High Technology R&D Pogram of China(2002AA305304)
文摘The surface morphology of GaN grown by MOCVD on GaN/Si template was studied.Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied.The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature.The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template.The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects.The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.
基金Supported by the Knowledge Innovation Project of Chinese Academy of Sciences, the National Natural Science Foundation of China under Grant No 60136020, the Special Funds for Major State Basic Research Project of China under Grant Nos G20000683 and 2002CB311903, and National High Technology Research and Development Programme of China under Grant No 2002AA305304.
文摘Mg-doped AlGaN and GaN/AlGaN superlattices are grown by metalorganic chemical vapour deposition （MOCVD） Rapid thermal annealing （RTA） treatments are carried out on the samples. Hall and high resolution x-ray diffraction measurements are used to characterize the electrical and structural prosperities of the as-grown and annealed samples, respectively. The results of hall measurements show that after annealing, the Mg-doped AIGaN sample can not obtain the distinct hole concentration and can acquire a resistivity of 1.4 ×10^3 Ωcm. However, with the same annealing treatment, the GaN/AlGaN superlattice sample has a hole concentration of 1.7 × 10^17 cm-3 and a resistivity of 5.6Ωcm. The piezoelectric field in the GaN/AlGaN superlattices improves the activation efficiency of Mg acceptors, which leads to higher hole concentration and lower p-type resistivity.
