Zone melt growth of GaAs for gamma ray detector applications

Vertical Zone Melt Growth (VZM) is being investigated as a technique for preparation of bulk GaAs crystals with applications as ambient temperature gamma ray detectors/spectrometers. Zone refining (repeated passes of a molten zone across a crystal) and zone levelling (one pass of a molten zone which is gallium rich) are being investigated for improving the purity of bulk GaAs and lowering the deep level donor defect (EL2) concentration. GaAs which has been zone refined and GaAs which has been zone levelled with a gallium rich melt have been grown, characterized and processed as detectors. In this paper, we discuss details of the VZM growth of GaAs and the crystalline and electronic properties achieved by zone levelling and zone refining.