Atomic Layer Epitaxy of GaAs and InAs

The saturation behavior of growth of GaAs and InAs by atomic layer epitaxy is studied. The growth rate is found to be strongly dependent on alkyl exposure time for the same total alkyl exposure per cycle. The longer the exposure time, the higher the saturated growth rate is. For short exposure, the growth rate saturates to a value less than one monolayer (ML)/cycle. Strong saturation of the growth rate to one ML/cycle is achieved for InAs at a growth temperature of 340°C with 3 sec of trimethylindium exposure. For GaAs, saturation of the growth rate to one ML/cycle is achieved at the growth temperature of 400°C with 10 sec of trimethylgallium exposure. At higher growth temperatures, the growth rate does not saturate but increases slowly with increasing exposure. The large physical size and finite decomposition time of the initial adsorbate are suggested as the cause for the dependence of ALE growth rate on alkyl exposure time.