Upconversion of photoluminescence due to subband resonances in a GaAs/AlAs multiple quantum well structure

We have investigated the upconversion of photoluminescence (PL) due to subband resonances in a simple GaAs(15.3 nm)/AlAs(4.5 nm) multiple quantum well embedded in a p–i–n diode structure. The systematic measurements of the PL spectra and the calculated results of the interband transition energies as a function of electric field strength reveal that the PL bands from the electron subbands with n=3 (E3) and n=4 (E4) sharply appear under the first-nearest-neighbor resonance conditions between the E1 and E3 subbands and the E1 and E4 subbands, respectively, owing to the carrier injection to the E3 and E4 subbands from the E1 subband. This result indicates that the resonant tunneling due to the subband resonance is a dominant mechanism for the carrier population in the higher lying subbands. Utilizing these subband resonances, we have demonstrated the upconversion of PL from the E3 and E4 subbands under the excitation condition of the fundamental interband transition between the E1 and the n=1 heavy-hole subbands.