Optical Properties and Carrier Transport in a Biased GaAs/AlAs Asymmetric Quintuple-Quantum-Well Superlattice

Photoluminescence (PL) properties and carrier transport in a GaAs/AlAs asymmetric quintuple-quantum well superlattice (AQQW-SL) were investigated. Since AQQWs are separated by very thin AlAs barriers, various carrier transport phenomena are expected due to the strong coupling of wave functions between the Γ states in the GaAs QWs and the X states in the AlAs barriers. A 20-period AQQW was embedded in the i-layer of a pin diode. A PL signal between the ground Γ and the heavy hole (hh) states was observed around 740 nm. However, another PL branch was observed at about 665 nm around 6 V. Based on the numerical calculation of the Γ and X wave functions, the electron transport from the X state in the thick AlAs barrier (X11) to the Γ state in the third QW (Γ31) occurs at 6.1 V. Thus, a PL signal at 665 nm can be attributed to the recombination between Γ31 and hh11.