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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 AlxGa1−xN and single AlN buffer layers grown on a Si (111) substrate by metal-organic vapour phase epitaxy (MOVPE). The results show that a 1000 nm GaN epilayer with a perfect crystal quality (χ min = 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 113 axis in the (100) plane and the conventional HRXRD θ−2θ scans normal to GaN (002) and (112) 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).

The composition, elastic strain and structural defects of InGaN/GaN multiple quantum wells (MQWs) are comparatively investigated by using x-ray diffraction (XRD), transmission electron microscopy and Rutherford backscattering/channelling. The InGaN well layers are fully strained on GaN, i.e. the degree of relaxation is zero. The multilayered structure has a clear defined periodic thickness and abrupt interfaces. The In composition is deduced by XRD simulation. We show how the periodic structure, the In composition, the strain status and the crystalline quality of the InGaN/GaN MQWs can be determined and cross-checked by various techniques.

Epitaxial ZnO films are grown on Al2O3 (0001) by the MOCVD method. These films are high quality wurtzite crystals with (0001) orientation. Big hexagonal crystallites (diameter from several decades to 100 μm) are found on the surface. Inside these crystallites, a stronger luminescence is observed compared with the plain area. Transmission electronic microscopy reveals that the film is thicker inside the hexagonal crystallites than the plain area, and some crystallites are not connected with each other and are slightly rotated with respect to their neighbours.

AlxGa1−xN/GaN heterostructures are grown on c-sapphire with the Al composition x from 0.2 to 0.4 and thicknesses from 20 nm to 30 nm. The lattice parameters a and c are determined from 2θ/ω scan. The AlGaN layers are found to be under tensile strain by using x-ray diffraction. Vegard's law induces a large deviation in Al composition determination by only considering the linear relationship between one lattice parameter (a or c) and Al composition. The accurate determination of Al composition is only possible with consideration of both the lattice parameters a and c, by assuming the tetragonal distortion in the AlGaN layer. Additionally, the results obtained from x-ray diffraction are verified by Rutherford backscattering.

Ga(In, Al)N alloys are used as an active layer or cladding layer in light emitting diodes and laser diodes. x-ray diffraction is extensively used to evaluate the crystalline quality, the chemical composition and the residual strain in Ga(Al,In)N thin films, which directly determine the emission wavelength and the device performance. Due to the minor mismatch in lattice parameters between Ga(Al, In)N alloy and a GaN virtual substrate, x-ray diffraction comes to a problem to separate the signal from Ga(Al,In)N alloy and GaN. We give a detailed comparison on different diffraction planes. In order to balance the intensity and peak separation between Ga(Al,In)N alloy and GaN, (0004) and (1015) planes make the best choice for symmetric scan and asymmetric scan, respectively., 9 pages, 5 figures

Mg+ and Mg++P+ were introduced into GaN by ion implantation. The structure and crystalline quality of the GaN samples were analysed by Rutherford backscattering and channelling spectrometry before (χmin = 1.6%) and after implantation (χmin = 4.1%). X-ray diffraction reveals the existence of implantation-induced damage in the case of post-implantation followed by rapid thermal annealing. The resistivity, average factor, carrier concentration and carrier mobility were measured by the Hall effect. The transformation from n-type to p-type for GaN was observed.