IMPROVEMENT OF STOICHIOMETRY IN SEMIINSULATING GALLIUM-ARSENIDE GROWNUNDER MICROGRAVITY

A semi-insulating (SI) GaAs single crystal was recently grown in a ret rievable satellite. The average etch pit density (EPD) of dislocations in the crystal revealed by molten KOH is 2.0 x 10(4) cm(-2), and the highest EPD is 3.1 x 10(4) cm(-2) This result indicates a quite good h omogenity of the EPD which is much better than the ground-grown crysta ls. A similar better homogenity of the stoichiometry i.e., the [As]/([ As] + [Ga]) ratio has been found in the space-grown SI-GaAs single cry stal studied nondestructively using a new mapping method based upon X- ray Bond diffraction. The average stoichiometry in the space-grown cry stal is 0.50007 with mean-square deviation of 6x10(-6), while the aver age stoichiometry in ground-grown SI-GaAs crystal is more than 0.50010 . (C) 1998 Elsevier Science B.V. All rights reserved.