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A deep state possessing similar properties to those reported for DX centers in the AIGaAs system has been observed at atmospheric pressure in GaSb moderately doped with sulfur. The first detailed deep level transient spectroscopy study of this material has revealed a large energy barrier to electron capture and a correspondingly small capture cross section for this deep level. The deep level activity of selenium-and tellurium-doped GaSb has also been investigated.

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The incorporation of erbium from a solid source Into molecular beam epitaxy (MBE) Si and SiJFe alloys grown at substrate temperatures of 500 "C and 700 "C has been studied by photoluminescence, electrical measurements, secondary-ion mass spectrometry (SIMS). Rutherford backscattering (RBS) and transmission electron microscopy (TEM). Erbium concentrations between 10'' and IOz2 cm-3 were obtained but the maximum photoluminescence intensity was from samples with an erbium concentration of 2 x 10'8cm-3. Above this concentration the onset of erbium precipitation could just be observed by TEM. We found no shallow donors or acceptors attributable to erbium but we observed a high concentration of deep acceptors with an activation energy of 360 meV; these may be due to impurities in the erbium source rather than being directly related to the rare earth, Implantation with oxygen is found to enhance the Er3+-related photoluminescence signal when measured at temperatures greater than 77 K but to have little effect on the low-temperature luminescence. A detailed study of the temperature dependence of the luminescence reveals three quenching mechanisms with average activation energies of approximately 5, 20 and 130 meV. W e attribute the first two to de-excitation effects in the matrix, and the last to processes competing with the internal 4 f transition.niques. A shallow implant also makes some optical '237

We present results of a study using metal-organic vapor phase epitaxy (MOVPE) to synthesize thin films of cubic GazSe3 on both nearly lattice matched GaP and mismatched GaAs substrates. We find that trimethylgallium (TMGa) pre-reacts with the hydride HzSe in the gas phase to yield films which are only partially epitaxial and that the combination of TMGa with ditertiarybutylselenide produces films of the best crystal quality under steady state flow conditions. We also show that GaAs is an unsuitable substrate for MOVPE growth of gallium selenide due to exchange reactions at the interface leading to poorly bonded films.