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In this study, a very thin Ni/Au bilayer metal film was prepared by electron beam evaporation and thermal alloying to form ohmic contact on p-type GaN film. After thermal alloying, the currentvoltage (I-V) characteristic of Ni/Au contact on p-type GaN film exhibited ohmic behavior. The Ni/Au contacts showed a specific contact resistance of 1.7ϫ10 Ϫ2 ⍀ cm 2 at an alloying temperature of 450°C. In addition, the light transmittance of the Ni/Au ͑2 nm/6 nm͒ bilayer on p-type GaN was measured to be around 85% at 470 nm. These results suggest that a suitable metallization technology for the fabrication of light emitting devices can be achieved.

In this work indium tin oxide (ITO) films were prepared using electron beam evaporation to form Schottky contacts on n-type GaN films. The thermal stability of ITO on n-type GaN was also investigated by annealing the samples at various temperatures. In addition, current–voltage (I–V) measurements were taken to deduce the Schottky barrier heights. Owing to the large series resistance, the Norde method was used to plot the F(V)–V curves and the effective Schottky barrier heights were determined as well. The effective Schottky barrier heights were 0.68, 0.88, 0.94, and 0.95 eV for nonannealed, 400, 500, and 600 °C annealed samples, respectively. Results presented herein indicate that an increase of the barrier heights may be attributed to the formation of an interfacial layer at the ITO/GaN interface after annealing.

A detailed optical study of the metastable III/V semiconductor alloy InP1−xSbx is presented. InP1−xSbx layers are grown throughout the entire compositional range by atmospheric pressure organometallic vapor phase epitaxy on InP, InAs, and InSb substrates. Composition and strain are measured by combined electron microprobe analysis and x-ray diffractometry. The dependence of band gap on composition is experimentally established for the first time from absorption spectra measured at 10 and 300 K. The resultant value of the band-gap bowing parameter is 1.52±0.08 eV, independent of temperature. The absorption spectra show the InP1−xSbx layers to have long band tails, which extend further into the gap as the Sb concentration is increased. The band tails are induced by compositional clustering. Photoluminescence (PL) spectra are measured between 10 and 300 K. The PL peaks are assigned to recombination between carriers occupying band-tail states or to recombination via deep centers in the gap.

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