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We have studied the influence of an AlGaN insertion layer in a GaN quantum well on the light emission from a strained GaN/AlGaN multiple-quantum well system. The structural properties of GaN/AlGaN multiquantum wells of the same composition were studied by using the reciprocal space mapping and simulation techniques of high-resolution x-ray diffraction. The lattice constants along the in-plane direction determined from the (1 0 5) reciprocal space maps were a = 3.161 A for normal multiquantum wells and a = 3.152 A for interlayer multiquantum wells. The spatial localization of the quantum well emission was unambiguously determined by monochromatic cathodoluminescence measurements. This observation indicates that the blue emission near 2.96 eV in the interlayer multiquantum wells originates from the MQW region, rather than from a deep level in the GaN buffer layer. These transitions could be a quantum confined Stark effect due to the piezoelectric field caused by the strain between the well and barrier.

The thermal process of the growth of GaN-based semiconductors was analysed for two home-made horizontal reactors. The reactors were designed to make the ammonia gas flow in the opposite direction to the main gas flow. For two horizontal reactors different in dimension, the low Reynolds numbers of Re = 2.94 and 4.15 were chosen for stable laminar flow and the Rayleigh numbers governing the heat convection were optimized to the values of Ra = 6.0 and 76.2, respectively. The qualities of GaN and InGaN films were characterized by Hall effect measurement, x-ray diffraction and photoluminescence and compared with respect to the reactor dependency.

In order to realize ZnSSe/GaAs heteroepitaxial layers with lower defect density, we have introduced molecular beam epitaxy growth by a three-step temperature correction which takes account of the cell radiation and surface emissivity effects superposed on the Fabry - Perot interference oscillation in the pyrometric temperature. The optimum correction rates of growth temperature are determined by the analysis of double-crystal x-ray rocking curves, and an empirical profile for the control temperature as a function of growth time is proposed for the optimum ZnSSe growth. While the etch pit density is in normal molecular beam epitaxy growth, an etch pit density of , which is the lowest value known so far, is realized in ZnSSe/GaAs(100) epilayers grown by using the linearly corrected profile.

Shubnikov-de Haas and Van der Pauw Hall effect measurements on strained InAs0.6P0.4/InP one-side-modulation-doped quantum wells grown by metalorganic chemical vapour deposition have been performed in order to investigate the properties of an electron gas in an InAs0.6P0.4 single quantum well. Hall effect measurements showed that the mobility and the carrier concentration were 40800 cm2 V-1 s-1 and 1.43*1012 cm-2 at 1.5 K, respectively. The Shubnikov-de Haas measurements and fast-Fourier analyses clearly showed an oscillation frequency, which changes with the angle between the magnetic field and the surface normal, indicative of the occupation of the InAs0.6P0.4 potential well by two-dimensional electrons. The subband energies and energy wavefunctions were determined using the experimental results and a self-consistent method taking into account the exchange-correlation effects.