This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in...This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.展开更多
The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction （XRD） techniques, including out-of-plane XRD at special planes, in-plane grazing incid...The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction （XRD） techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping （RSM）. It is confirmed that the measurement of （204） reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more In atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 60506001,60776047,60976045 and 60836003)the National Basic Research Programme of China (Grant No. 2007CB936700)the National Science Foundation for Distinguished Young Scholars,China (Grant No. 60925017)
文摘This paper investigates the major structural parameters, such as crystal quality and strain state of （001）-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x- ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence t of （100） reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of-0.89 GPa.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60506001, 60776047, 60976045, and 60836003)the National Basic Research Programme of China (Grant No. 2007CB936700)the National Natural Science Foundation for Distinguished Young Scholars (Grant No. 60925017)
文摘The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction （XRD） techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping （RSM）. It is confirmed that the measurement of （204） reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more In atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.
