Deep defects in intermediate temperature molecular beam epitaxy grown GaAs and their role in current transport

Current transport in molecular beam epitaxy (MBE) GaAs grown at low and intermediate growth temperatures is strongly affected by defects. A model is developed here that shows that tunneling assisted by deep defect states can dominate, at some bias ranges, current transport in Schottky contacts to un-annealed GaAs material grown at the intermediate temperature range of about 400/spl deg/C. It is suggested that reduction of these defects by thermal annealing can explain lower current conduction at high biases in the annealed device as well as higher current conduction at low biases due to higher lifetime. Quenching of current by light in the as-grown material is shown and can also be explained based on occupancy of trap states. Identification of this mechanism can lead to its utilization in making ohmic contacts, or its elimination by growing tunneling barrier layers. This material finds wide-spread use in microwave and optical applications.