Photoluminescence quenching in reverse-biased ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As/GaAs quantum-well heterostructures due to carrier tunneling

The photoluminescence intensity of reverse-biased ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As/GaAs quantum wells decreases considerably with increasing electric field perpendicular to the quantum-well layers. We show that the photoluminescence intensity decrease is accompanied by an increase of the photocurrent, whose quantum efficiency is high. The phenomenon of photoluminescence quenching is therefore explained by the leakage of photogenerated carriers through the barrier layers rather than by enhanced nonradiative recombination processes within or in the vicinity of the quantum wells. We conclude that the photocurrent is determined by the tunneling of holes, and we apply a simple tunneling theory to interpret the observed data. A good agreement between theory and experiment is obtained by using the valence-band-edge discontinuity of Δ$E_v$/Δ$E_g$=0.20 at the ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As/GaAs heterojunction.