Comparative study of high and low temperature AlN interlayers and their roles in the properties of GaN epilayers prepared by means of metal organic chemical vapour deposition on (0001) plane sapphire substrates is c...Comparative study of high and low temperature AlN interlayers and their roles in the properties of GaN epilayers prepared by means of metal organic chemical vapour deposition on (0001) plane sapphire substrates is carried out by high resolution x-ray diffraction, photoluminescence and Raman spectroscopy. It is found that the crystalline quality of GaN epilayers is improved significantly by using the high temperature A1N interlayers, which prevent the threading dislocations from extending, especially for the edge type dislocation. The analysis results based on photoluminescence and Ruman measurements demonstrate that there exists more compressive stress in GaN epilayers with high temperature AlN interlayers. The band edge emission energy increases from 3.423 eV to 3.438 eV and the frequency of the Raman shift of E2(TO) moves from 571.3 cm-1 to 572.9 cm-1 when the temperature of AlN interlayers increases from 700 ℃ to 1050 ℃. It is believed that the temperature of AlN interlayers effectively determines the size, the density and the coalescence rate of the islands, and the high temperature AlN interlayers provide large size and low density islands for GaN epilayer growth and the threading dislocations are bent and interactive easily. Due to the threading dislocation reduction in GaN epilayers with high temperature AlN interlayers, the approaches of strain relaxation reduce drastically, and thus the compressive stress in GaN epilayers with high temperature AlN interlayers is high compared with that in GaN epilayers with low temperature AlN interlayers.展开更多
Rutherford backscattering (RBS)/channelling and high resolution x-ray diffraction (HRXRD) have been used to characterize the tetragonal distortion of a GaN epilayer with four Alx Ga1-xN and single AIN buffer layer...Rutherford backscattering (RBS)/channelling and high resolution x-ray diffraction (HRXRD) have been used to characterize the tetragonal distortion of a GaN epilayer with four Alx Ga1-xN and single AIN buffer layers grown on a Si (111) substrate by metal-organic vapour phase epitaxy (MOVPE). The results show that a 1000nm GaN epilayer with a perfect crystal quality (Xmin = 1.54%) can be grown on the Si (111) substrate in virtue of multiple buffer layers. Using the RBS/channelling angular scan around an off-normal (1213) axis in the (1010) plane and the conventional HRXRD θ - 20 scans normal to GaN (0002) and (1122) planes at the 0° and 180° azimuth angles, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer and different buffer layers, can be obtained respectively. The two experiments are testified at one result, the tetragonal distortion of GaN epilayer is nearly to a fully relaxed (eT = 0).展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60736033 and 60676048)
文摘Comparative study of high and low temperature AlN interlayers and their roles in the properties of GaN epilayers prepared by means of metal organic chemical vapour deposition on (0001) plane sapphire substrates is carried out by high resolution x-ray diffraction, photoluminescence and Raman spectroscopy. It is found that the crystalline quality of GaN epilayers is improved significantly by using the high temperature A1N interlayers, which prevent the threading dislocations from extending, especially for the edge type dislocation. The analysis results based on photoluminescence and Ruman measurements demonstrate that there exists more compressive stress in GaN epilayers with high temperature AlN interlayers. The band edge emission energy increases from 3.423 eV to 3.438 eV and the frequency of the Raman shift of E2(TO) moves from 571.3 cm-1 to 572.9 cm-1 when the temperature of AlN interlayers increases from 700 ℃ to 1050 ℃. It is believed that the temperature of AlN interlayers effectively determines the size, the density and the coalescence rate of the islands, and the high temperature AlN interlayers provide large size and low density islands for GaN epilayer growth and the threading dislocations are bent and interactive easily. Due to the threading dislocation reduction in GaN epilayers with high temperature AlN interlayers, the approaches of strain relaxation reduce drastically, and thus the compressive stress in GaN epilayers with high temperature AlN interlayers is high compared with that in GaN epilayers with low temperature AlN interlayers.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10375004 and 10575007, and the Bilateral Cooperation between China and Belgium under Grant No BIL04/05.
文摘Rutherford backscattering (RBS)/channelling and high resolution x-ray diffraction (HRXRD) have been used to characterize the tetragonal distortion of a GaN epilayer with four Alx Ga1-xN and single AIN buffer layers grown on a Si (111) substrate by metal-organic vapour phase epitaxy (MOVPE). The results show that a 1000nm GaN epilayer with a perfect crystal quality (Xmin = 1.54%) can be grown on the Si (111) substrate in virtue of multiple buffer layers. Using the RBS/channelling angular scan around an off-normal (1213) axis in the (1010) plane and the conventional HRXRD θ - 20 scans normal to GaN (0002) and (1122) planes at the 0° and 180° azimuth angles, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer and different buffer layers, can be obtained respectively. The two experiments are testified at one result, the tetragonal distortion of GaN epilayer is nearly to a fully relaxed (eT = 0).