Compensation of charge fluctuations in quantum wells with dual tunneling and photon-assisted escape paths

Abstract

In our previous article [D. H. Huang, A. Singh, and D. A. Cardimona, J. Appl. Phys. 87, 2427 (2000)], we explained the experimentally observed zero-bias residual tunneling current [A. Singh and D. A. Cardimona, Opt. Eng. 38, 1424 (1999)] in quantum-well photodetectors biased by an ac voltage. In this article, we extend our theory to include the photoemission current and reproduce our recent findings on the dynamical drop of photoresponsivity Rph(t) from its static value Rph0 in quantum-well photodetectors as a function of the chopping frequency of the incident optical flux. In this theory, we derive a dynamical equation for a nonadiabatic space-charge field Ena(t) in the presence of an applied electric field Eb(t) and an incident optical flux Φop(t). From it, a compensation of the charge fluctuations in quantum wells is predicted as a result of dual tunneling and photon-assisted escaping paths. We also find a suppression of the nonadiabatic deviation of Rph(t) from Rph0 due to a charge-depletion effect in the quantum wells.