Effects of carrier-storage layer of InAs/GaAs short period superlattice on photocurrent in GaAs/GaAlAs multi-quantum well structure

Negative differential characteristics in the relations between photoinduced currents and forward bias voltages are investigated considering accumulations of photogenerated carriers in a storage layer on a GaAs/GaAlAs multi-quantum well structure. The nonlinear characteristics become obvious when the storage layer is an InAs/GaAs short period superlattice and can be observed at 300 K under weak photoexcitations (e.g., 2.5 mW/cm(2)). On the other hand, the phenomenon is extremely reduced in the case of a storage layer of an InGaAs alloy or InAs, and disappears without the storage layer. These results correspond with the differences of carrier lifetime in the storage layer. The enhanced negative differential characteristics can be due to the smaller trap densities and the larger electron mobility in the storage layer of the InAs/GaAs short period superlattice. Finally, the applications of the characteristics to the selectivity functions of visual neurons-are discussed. (C) 1996 American Institute of Physics.