Thermal Stability of a Short Period AlAs/n-GaAs Superlattice

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Abstract
Stability was examined for an AlAs/n-GaAs superlattice (SL), whose Si donors were confined to the GaAs layer. The SL was grown by MBE at 520°C and was annealed at a temperature (T a) from 560 to 800°C. Up to T a=600^°C, no sign of Al-Ga mixing was observed, and the amount of a DX centerlike trap was proportional to exp (-0.65 eV/k T a). The increase in the trap was due to Si diffusion to the AlAs/GaAs interfaces with the activation energy of 1.3 eV for its diffusion coefficient. As increasing T a above 650°C, Al-Ga mixing was accelerated and a decrease in carrier concentration and an increase in persistent photoconductivity were observed.