High purity GaAs grown by the hydride vpe process

Epitaxial growth of high purity undoped GaAs by the hydride VPE process with electrical properties comparable to the best AsC₃ VPE results have been achieved. Background carrier concentration n₇₇ = 2 × 10¹³/cc and mobility μ₇₇ = 201,000 cm²/Vsec was achieved by careful control of the growth process. The effects of HC1 partial pressure over the Ga source, arsine and secondary HC1 partial pressures were Investigated. Use of secondary HC1 was found to result in compensated layers and hence should be avoided for high purity layers. Aging of the liquid HC1 source in its stainless steel container over extended time period was also found to result in degradation of epilayer purity due to increased acceptor contamination. Low temperature photoluninescence and far infra-red photoconductivity measurements were used to determine the residual acceptors and donors respectively. The major acceptors found were carbon and zinc. The major donor was sulfur. Key works: GaAs, hydride VPE growth, high purity layers, impurity identification