Population inversion between subbands in simple periodical GaAs/AlAs superlattices

Photoluminescence (PL) from type-I GaAs-AlAs superlattices (SLs) have been studied under an electric field. In such SLs the AlAs layer, which is the barrier for the Γ subbands, is the quantum well for the X electron subbands. The X subbands in the AlAs barriers have a large density of subbands, and have a great influence on carrier transport even in type-I GaAs/AlAs SLs. Furthermore, the X subbands can be expected to be useful for carrier injection into a higher Γ subband using X-Γ resonance because PL from transitions between higher Γ subbands and hhl has been observed. Intersubband population inversion in simple periodical GaAs/AlAs SLs is presented using X-Γ resonance. Interband PL measurement and calculation of the overlap integral between electrons and hole subbands confirm the intersubband population inversion. Carrier injection into higher subbands using X-Γ resonance is expected to be useful for achieving simple quantum cascade laser structures