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Electron transport in a short As/GaAs superlattice

We report an experimental and theoretical study of electron transport in short ( nm) As/GaAs n-type superlattices. In order to make the results of this investigation relevant to quantum-well infrared photodetectors, our devices had wide barriers at the contacts to reduce dark current. Transport involved both thermal and tunnelling components, in general, throughout the temperature range 77-300 K. At a critical high current superlattice domain formation associated with tunnelling negative differential resistance was observed in some of our devices. Standard theoretical expressions were used for the thermal and tunnelling components in each section of the device. At higher biases Fowler-Nordheim tunnelling was used to explain the rapid increase in current with voltage. The critical roles of well capture, confined level broadening and built-in voltages were identified. Satisfactory agreement between theory and experiment was obtained and this allowed an estimate of level broadening to be made.