Atomic layer epitaxy of GaAs using GaBr and GaI sources

Halogen transport atomic layer epitaxy (ALE) of GaAs using GaBr and GaI is investigated by means of two in situ monitoring methods: the gravimetric method and the surface photo-absorption (SPA) method. It is shown that the growth of one monolayer/cycle is possible in both the GaBr and GaI systems under a wide range of growth conditions at low temperature, while at high temperature, the decrease of the growth rate is observed due to the weak adsorption force of GaBr and GaI on GaAs surface. In addition, in both methods, we have observed the slow rate of HBr desorption during H2 purge after GaBr supply in comparison with the GaCl system. The reaction mechanism that proceeds on the GaAs surface in GaBr and GaI sources is discussed.