Electrical properties and deep levels in bulk solution grown GaAs crystal

Abstract

Electrical and photoelectrical properties, deep levels spectra and microcathodoluminescence spectra were measured for bulk high-resistivity GaAs samples grown from Ga-rich solution by a synthesis solute diffusion technique. It is shown that the main portion of the grown crystal is high-resistivity p-type with electrical properties determined by deep hole traps with the level near 0.43 eV from the valence band edge. The density of these 0.43 eV hole traps was shown to decrease with increasing distance from the crystallization front and the traps were associated with the deep hole traps observed earlier in Ga-rich liquid-phase-epitaxy-grown films. The single crystalline end portion of the crystal was semi-insulating n-type with a very low (some 10 14 cm −3) concentration of midgap EL2 donors. This end portion of the crystal was characterized by a very high photosensitivity. Possible advantages of the use of such material in radiation detectors are briefly discussed.