Atomic layer epitaxy of device quality GaAs

Device quality GaAs was grown in a conventional organometallic chemical vapor deposition reactor, using sequential group III (trimethylgallium, TMG) and group V (arsine) reactant gas exposures typical of atomic layer epitaxy (ALE). The results show that, at a given temperature, impurity (e.g., carbon) incorporation is controlled by the effective V/III ratio at the growing surface, which is determined by the sequence used in the growth cycles. This effect, specific to ALE, is quantified by solving the diffusion equation that describes concentration transients at the growing surface. Detailed photoluminescence experiments identified C and Mg as the residual acceptors and Ge as the sole residual donor in a 3×10¹⁵ cm^{- 3} n-type background layer with mobilities of 5600 cm²/V s at room temperature and 35 000 cm²/V s at 77 K. A higher purity sample showed reduced levels of Ge, with traces of S, Si, and Te donors and only C acceptors.