Identification of room temperature photoluminescence in pseudomorphic modulation-doped AlGaAs/InGaAs/GaAs quantum wells

Abstract

Room temperature photoluminescence in δ-doped pseudomorphic AlGaAs/InGaAs/GaAs quantum wells is investigated. The electron and hole subband structure and optical transition matrix elements are calculated by a self-consistent theoretical method. Separations of the calculated conduction subband levels and valence subband levels reveal that the dominant emissions are due to the transitions from the second electron subband to the first heavy-hole subband, the first electron subband to the first heavy-hole subband, and the first electron subband to the second heavy-hole subband. The calculation also predicts that the transition energies shift to lower energies with the increase of the δ-doping level. This is accounted for by the lowering of the confined levels originating from electrostatically induced band bending. The calculated transition matrix elements demonstrate that transitions with different electron and hole subband indices, i.e., forbidden pairs, are preferred. The relative magnitudes of the squared optical matrix elements for the transitions from the first and second electron subbands to the first heavy-hole subband are analyzed as functions of separations of the first two electron subbands and the first two heavy-hole subbands, respectively. The results show that the 2-1 pair has a larger oscillator strength than the 1-1 and 1-2 pairs in agreement with observations.