GaN films with different thicknesses of Al composition graded AlGaN buffer are grown on substrates of Si(111)by metal-organic chemical vapor deposition(MOCVD).The thicknesses of graded AlGaN buffer are fixed at 200 nm...GaN films with different thicknesses of Al composition graded AlGaN buffer are grown on substrates of Si(111)by metal-organic chemical vapor deposition(MOCVD).The thicknesses of graded AlGaN buffer are fixed at 200 nm,300 nm,and 450 nm,respectively.Optical microscopy,atomic force microscopy,x-ray diffraction,and Raman spectroscopy are employed to characterize these samples.We find that the thickness of the graded AlGaN buffer layer plays a key role on the following growth of GaN films.The optimized thickness of the graded AlGaN buffer layer is 300 nm.Under such conditions,the GaN epitaxial film is crack-free,and its dislocation density is the lowest.展开更多
The strain in GaN epitaxial layers grown on 611-SiC substrates with an AIN buffer by metalorganic chemical vapor deposition is investigated.It is found that the insertion of a graded AlGaN layer between the GaN layer ...The strain in GaN epitaxial layers grown on 611-SiC substrates with an AIN buffer by metalorganic chemical vapor deposition is investigated.It is found that the insertion of a graded AlGaN layer between the GaN layer and the AIN buffer can change the signs of strain.A compressive strain in an overgrown thick(2μm)GaN layer is obtained.High-resolution x-ray diffraction,Raman spectroscopy and photoluminescence measurements are used to determine the strain state in the GaN layers.The mechanism of stress control by inserting graded AlGaN in subsequent GaN layers is discussed briefly.展开更多
基金Supported by the National High-Technology Research and Development Program of China under Grant Nos 2011AA03A112 and 2011AA03A106the National Natural Science Foundation of China under Grant Nos 60890192,50872146 and 60877006.
文摘GaN films with different thicknesses of Al composition graded AlGaN buffer are grown on substrates of Si(111)by metal-organic chemical vapor deposition(MOCVD).The thicknesses of graded AlGaN buffer are fixed at 200 nm,300 nm,and 450 nm,respectively.Optical microscopy,atomic force microscopy,x-ray diffraction,and Raman spectroscopy are employed to characterize these samples.We find that the thickness of the graded AlGaN buffer layer plays a key role on the following growth of GaN films.The optimized thickness of the graded AlGaN buffer layer is 300 nm.Under such conditions,the GaN epitaxial film is crack-free,and its dislocation density is the lowest.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50872146 and 60890192/F0404.
文摘The strain in GaN epitaxial layers grown on 611-SiC substrates with an AIN buffer by metalorganic chemical vapor deposition is investigated.It is found that the insertion of a graded AlGaN layer between the GaN layer and the AIN buffer can change the signs of strain.A compressive strain in an overgrown thick(2μm)GaN layer is obtained.High-resolution x-ray diffraction,Raman spectroscopy and photoluminescence measurements are used to determine the strain state in the GaN layers.The mechanism of stress control by inserting graded AlGaN in subsequent GaN layers is discussed briefly.
