Low stacking-fault density in ZnSe epilayers directly grown on epi-ready GaAs substrates without GaAs buffer layers

We report a remarkably low stacking-fault density in ZnSe epilayers directl y grown on commercial epi-ready GaAs (001) substrates without GaAs buffer l ayer growth. It is found that proper pregrowth treatments on epi-ready GaAs (001) substrates to obtain clean surfaces are crucial for two-dimensional layer-by-layer growth and suppression of stacking fault generation. Chemica l etching using a NH4OH-based solution is found to reduce not only the thic kness of the oxide layers but also the ratio of Ga2O3 to As2O3 to about hal f of that before etching. A clean GaAs (001) surface characterized by a (4 x 1) reconstruction in the present case is obtained after thermal cleaning followed by Zn pre-exposure. Reflection high-energy electron diffraction in tensity oscillations with more than 50 periods are observed even from the v ery beginning of ZnSe growth on GaAs substrates cleaned as such. The stacki ng fault density in such a ZnSe layer is in the low-10(5) cm(-2) range. (C) 2001 American Institute of Physics.