A new surface treatment technique of GaAs substrates prior to molecular-beam epitaxial growth has been developed, which provides a low temperature thermal annealing in vacuum and an As-passivated surface. The As passivated surface was obtained by immersing a GaAs substrate in a 50% HF solution. Auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) studies of the As-passivated GaAs substrates have been performed. The suitable thermal treatment temperature of the As-passivated GaAs substrate in vacuum was found to be lower than 500°C since thermal facets were not developed on the surface and the RHEED pattern on this clean surface exhibited a 2×1 As reconstructed structure. From the compositional profile of As-passivated GaAs substrate measured with AES and the thermal treatment experiment, it was found that the As passivating layer consisted of an As layer and an As oxide one.
Organic L-Arginine Phosphate Monohydrate (LAP) forms a new promising nonlinear op-tical crystal as a frequency converter for a high power laser. LAP crystals are generally grown from aqueous solutions and microbes breed more readily in LAP solutions than in KDP solutions. The carcases of these micro-bes or their pieces are entrapped in LAP cry-stals during growth. We have succeeded in measuring the amount of microbes which were entrapped in LAP crystals by using the chromogenic Limulus Test. It was found that the carcasses or their pieces were entrapped in a LAP crystal with a density two orders higher than in a KDP crystal.