Photoluminescence Properties Affected by Carrier Transport between X and Different First Excited States Originating from Interface Imperfection in GaAs/AlAs Multi-Quantum Wells

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The authors investigated the electric-field dependence of photoluminescence (PL) spectra in a GaAs/AlAs multi-quantum well (MQW) structure, in which QWs with different thicknesses coexist. PL properties in this sample are chiefly determined by the coexistence of 21-monolayer (ML) and 23-ML QWs, because the islands of 22-ML QWs are too small to have an effect on radiative processes. Two PL signals are found in the shorter-wavelength region, caused by X1–$\Gamma 2$ resonances, because the different thicknesses of GaAs QWs lead to different resonant voltages and wavelengths. We also estimated the carrier densities of excited states from the observed two PL intensities and by calculations of overlap integrals of wave functions between electron and heavy-hole states. This result clearly indicates that the carrier density in the $\Gamma 2$ in the 21-ML QW becomes larger than that in the 23-ML QW when the X1–$\Gamma 2$ resonance of the 21-ML QW occurs. This demonstrates that interface imperfection creates novel carrier transport paths and affects carrier densities as well as optical properties in excited states in MQW structures.
2008-01-25