PSEUDO-NEGATIVE PHOTOCURRENT SPECTROSCOPY IN GAAS-ALAS SUPERLATTICES

Pseudo-negative photocurrent spectra, i.e., the appearance of a minimu m in photocurrent at an absorption maximum, are experimentally studied at different temperatures and excitation intensities in GaAs-AlAs sup erlattices on GaAs substrates. Superlattice and substrate are isolated by a thick Al0.3Ga0.7As barrier, but electrically connected through p enetrating contacts. A simple model is proposed for the analysis of th e conditions which can lead to pseudo-negative photocurrent in this sa mple configuration. The radiative recombination of the carriers in the superlattice was found to be the main process determining the sign of the photocurrent at an absorption maximum. (C) 1996 American Institut e of Physics.