Current transport in as-grown and annealed intermediate temperature molecular beam epitaxy grown GaAs

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Abstract
Molecular beam epitaxy (MBE) GaAs grown in the intermediate temperature range of about 400 °C may provide combination of low lifetime, high resistivity, and high mobility. We compare current conduction in unannealed and annealed material grown at 400 °C by fabricating photodetectors on substrates grown between temperature ranges of 250–500 °C. The unannealed version of the device grown at 400 °C shows substantial difference of conduction properties in dark and under light. It is shown that while at low biases the unannealed material may be semi-insulating, at high biases more current is conducted than in annealed material. We attribute this to the effect of intergap states on current conduction and suggest that defect state assisted tunneling is the dominant current transport mechanism in these ranges. Quenching of response by light suggests that occupancy of traps can eliminate their role in current conduction.

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