Optical properties of CuInSe2 (CIS) films grown on (001) GaAs by molecular beam epitaxy (MBE) have been investigated by means of low temperature photoluminescence (PL) spectroscopy. Distinct emission lines including a bandedge emission were observed reproducibly from Cu-rich films, indicating high crystalline quality. Such well-defined PL spectra have made possible the extensive characterization of radiative recombination processes through the intrinsic defects in this material; some of the emission lines were attributed to phonon replicas with a phonon energy of 28–29 meV for the first time. PL spectra were found to be very sensitive to the MBE growth parameters such as substrate temperature, suggesting dominant defects in CIS epitaxial films can be controlled by varying the growth conditions.

No abstract

InN was epitaxially grown on (0001) α-Al2O3 substrates by the halogen transport method. Surface treatment of the substrate by a H2+Br2 gas (passed over In) just before the growth was essential for obtaining the epitaxial layers of InN. Arrays of extra spots were observed in the reflection electron-diffraction patterns of thin InN films. The extra spot arrays could be explained from the viewpoint that the crystal film was composed of twins. In these twin structures, the twinning planes were (7̄ 12 5̄ 0) and (1̄ 1̄ 20 9̄ 0). These extra spots ultimately disappeared with prolonged growth time. This result shows that as the growth proceeds, crystallites having a predominant orientation overwhelm other crystallites.

Single-crystal CdS (wurtzite-type) layers were prepared by vapor growth technique on the (001), (110), (112), and (221) faces of zinc-blende-type crystals such as GaP, GaAs, InAs, and CdTe in hydrogen atmosphere. Deposition temperatures were ranging from 620 to 740°C. The layer thicknesses were up to 20 μm. Relations of crystallographic orientation between the grown layers of CdS and the substrates were studied. It was found that (1) the [0001] a axis of CdS was nearly parallel to the [111] a axis of the substrate and (2) the (112̄0) face of CdS deposited on the faces except for (112) was parallel to the (11̄0) face of the substrate, and the (112̄0) face of CdS deposited on the (112) face was not always parallel to the (11̄0) face. Angles between the [0001] a and [111] a axes were a few degrees (up to 3°) and they depended both on substrate materials and orientations of the substrate surfaces. The dislocation model of small-angle grain boundaries was applied to interpret the result. It was found that CdS crystals are grown on crystallographic planes of zinc-blende-type materials in such a way that the interfacial mismatch between close-packed planes of CdS and the substrates vanishes.

Gallium nitride phosphide single crystals having the maximum composition of x∼0.09 were epitaxially deposited on (0001) sapphire substrates. The growth was carried out by the vapor phase reaction of the Ga-Br2-PH3-NH3-N2 system. The above maximum composition was attained at a substrate temperature of 980°C.