Single crystal cubic or hexagonal GaN thin films have been grown on various substrates, using a modified gas source MBE technique. A standard effusion cell was employed for the evaporation of gallium. A compact electron cyclotron resonance plasma source was used to activate the nitrogen prior to deposition. The films were examined by transmission electron microscopy. The major defects in the wurtzite GaN were double positioning boundaries, inversion domain boundaries, and dislocations. The zinc-blende GaN showed microtwins, stacking faults, and dislocations. The connection between the observed structural defects and the poor electrical properties of GaN is noted.

Studies on the cubic boron nitride (cBN) crystals grown by the temperature difference method at high pressure are reviewed. The electron beam induced current measurement, the electrical measurement, and the optical measurement demonstrated that the cBN is a good potential candidate as a wide-gap semiconductor material. The Raman spectrum and the reflectance and transmittance spectra of the cBN were obtained. The crys-tallographic polarity of cBN crystals was directly determined from the Rutherford backscattering spectroscopy (RBS).

The RBS experiment showed that the (111) surface which adjoins to the (100) surface at an obtuse angle so that the edge between the (111) and the (100) is parallel to the <110> direction of striations on the (100) face is a triply bonded nitrogen-terminating face. The result seems to disagree with that derived from other semiconductor compounds.

In cubic boron nitride made by high pressure and high temperature technique in our institute, we have found three luminescence bands in the ultraviolet and the short visible region at room temperature by cathode-ray excitation. They are: a band having vibrational structure and ascribable to undoped state of the crystal, a band ascribable to p-type doping and a band ascribable to n-type doping. Discussion is made on differences between the injection luminescence and the cathodoluminescence. Potentialities and difficulties in realizing the potentialities of cBN for optoelectronic applications are discussed.

Raman scattering measurements are used to distinguish between amorphous and crystalline phases in sputter deposited boron nitride coatings and bulk materials. Changes in vibrational line frequency and linewidth can be attributed to differences in particle size or inherent strain which can be quantified from pressure-dependent measurements of the bulk material. The response of the Raman-allowed E2g modes (hexagonal phase) to temperature is described by a forced dampeg harmonic oscillator model from which the intra- and interplanar lattice thermal expansion can be estimated.

Indium nitride thin films have been deposited using reactive rf-magnetron sputtering and characterized by their electrical, structural and morphological properties. Films have been prepared on fused quartz and (0001) sapphire. Films deposited on sapphire at temperatures from 50–300°C are typified by a slowly increasing mobility and a transition from mixtures of epitaxial and textured grains to complete epitaxy. Comparisons of films deposited on quartz and sapphire (with two different surface preparations) indicates that electrical mobility is enhanced by the epitaxial nature of the material deposited on sapphire and that a higher quality surface finish results in superior films. Somewhat above 300°C the morphology of the epitaxial films changes from continuous to granular, with a concomitant loss in electrical connectivity. This manifests itself as a sharp rise in the resistivity of the film and hence a sharp decline in the mobility. The carrier concentration shows a general decline as the substrate temperature is increased, indicating that the mechanism of mobility degradation is probably not due to thermally induced nitrogen vacancy formation but more likely to unintentional oxygen doping. This is in accord with the surface oxidation observed in the films using Auger electron spectroscopy.

The morphology of rf-sputtered films of the wide bandgap semiconductor InN on a variety of substrates over a range of temperatures have been studied by X-ray diffraction (XRD) and scanning tunneling microscopy (STM). For films deposited on fused quartz and the (111) face of silicon, there is a transition from an off-normal inclination to a fully textured (0001) film with increasing substrate temperature. In contrast, films deposited on the (0001) face of sapphire are textured or heteroepitaxial depending on the substrate temperature. For the heteroepitaxial domains, the rotation of the reciprocal lattice of InN by 30° to that of the sapphire substrate was established by X-ray precession photography. Finally, STM has proven to be a practicable method for non-destructively determining the substrate and temperature dependence of the grain size and surface roughness of these textured and heteroepitaxial films.

This paper describes growth morphology and structure of rfmagnetron sputtered thin films of InN, studied by plan-view transmission electron microscopy (TEM) and by scanning electron microscopy (SEM). Films deposited on TEM grids, (0001) sapphire, (111) silicon and amorphous quartz were prepared for TEM by mechanical abrasion of the substrate followed by sputter etching. At low deposition temperatures (<400°C), films consisted of small, basal-oriented, columnar grains. Above 500°C, growth consisted of larger, faceted, basal-oriented, mesa-island grains. Observations of growth morphology and defect structure are correlated with structural, compositional and electrical properties.

The crystal growth, characterization and various characteristics such as electrical, thermal and semiconducting properties of boron phosphide (BP) single crystalline wafers made by chemical vapor deposition technique are summrized. It is demonstrated that Schottky diode using single crystal and thermoelectric device employing sintered polycrystal are promising application for electronic materials.

The solid phase reactions of Ni thin films with refractory wide bandgap semiconductor BP(100) were investigated both in the thermal process and the ion beam induced process with RBS, AES, XRD and XPS. In the thermal reaction process, reactions of Ni thin films with BP started around 350°C. Transient metastable phases were observed between 400°C and 450°C. The formation of the fully reacted crystalline phase with the mixture of NiB and Ni3P was observed at 450°C. At elevated temperatures above 600°C, mixture of phases with less Ni content was found to be formed. For the ion beam induced process inhomogeneous reaction was observed at LN2 and the reaction at RT showed an amorphous phase with the same composition as the first thermal phase. The reaction at 200°C induced the same crystalline phase as the first thermal phase. The reacted layer thickness as a function of the ion beam fluence between RT and 300°C increased linearly with the fluence by showing the thermal dependence with an activation energy of Ea=O.31±O, O6eV above 100°C.

We report on radiation detectors fabricated from boron phosphide (BP) layers. These devices were fabricated by growing 1 to 10 μm thick layers of BP by chemical vapor deposition (CVD) on (100) oriented n-type silicon substrates. Ohmic contacts were applied to the Si (Au-Sb). Schottky barrier contacts (also Au-Sb) were applied to the BP layer. The devices were tested as radiation detectors and were found to be capable of detecting individual 5.5 MeV alpha particles. With some improvements we hope to fabricate neutron detectors from these devices, making use of the very high cross-section of boron for thermal neutrons.

Thin films of aluminum nitride have been grown by metalorganic chemical vapor deposition (MOCVD) from diethylaluminum azide. Growth rates of AIN on Si(111) were monitored in-situ with laser interferometry. The growth rate was linear in the partial pressure of the reactant at high temperatures and sublinear at low temperatures. A simple surface reaction mechanism consistent with these observations has been proposed. Surface reaction kinetics and mechanism were further investigated by steady-state kinetic mass spectrometry. Parameters in the growth rate expression were determined by a nonlinear regression of growth rate data. A typical sample of AIN on B-plane sapphire showed a bandgap of about 5.2eV which was increased to 5.9eV upon annealing in nitrogen at atmosphere pressure.

There is an old puzzle associated with the series of compounds formed by first row elements, C, BN, and BeO: similar to the other members of the family of octet semiconductors, these compounds exist in dense phases like diamond and zincblende, or hexagonal diamond (lonsdaleite) and wurtzite; however, whereas C and BN also exist in low density graphitic phases, BeO does not.

In this paper we report the growth and characterization of wide bandgap chalcopyrite structure semiconductor ZnGeP2 epitaxial layers by open tube MOCVD and ZnGeP2 single crystals by high-pressure vapor transport (HPVT). The electrical and optical properties of these crystals have been investigated by Hall measurements, absorption spectroscopy, photoconductivity and photoluminescence spectroscopy. The onset of the absorption edge for HPVT ZnGeP2 at 1.99 eV is in accord with the pseudodirect bandgap of this material. Both the meltgrown crystals and epitaxial layers show extended band tailing in the transparency range of ZnGeP2 depending on the growth conditions. Recently we have shown that epitaxial ZnGeP2 films can be grown with excellent surface morphology by MOCVD on (111) GaP substrates. These films should be suitable for phase matched second harmonic generation utilizing CO laser radiation in thick film heterostructures.