Enhancement of nonradiative recombination due to resonant electron capture in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs quantum-well structures

Anomalous enhancement of the nonradiative recombination is revealed to appear due to the resonant electron capture in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs quantum-well (QW) structures when the nonradiative recombination centers preferentially trap holes. Annealing experiments have shown that the anomalous reduction of photoluminescence intensity previously reported, which was observed under resonant conditions where the well width is such that the energy of the highest bound state in QW’s lines up with the barrier band edge, is completely recovered after thermal treatment. We find that the result can be well explained by a model of a nonradiative process based on Shockley-Read recombination when we assume that the nonradiative recombination center traps holes more efficiently than electrons. The model shows that the nonradiative recombination is enhanced when the centers are half occupied with electrons. Because the electron trapping is slow, such a situation can be realized when efficient capture of barrier electrons into QW’s due to the resonant electron capture brings about a higher density of electrons than that of holes. The model also successfully explains the experimental result of the excitation intensity dependence of the photoluminescence intensity and it is shown that nonradiative recombination centers exist in the GaAs well layer.