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 b arrier for the Gamma subbands, is the quantum well for the X electron subba nds. 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 SL s. Furthermore, the X subbands can be expected to be useful for carrier inj ection into a higher Gamma subband using X-Gamma resonance because PL from transitions between higher Gamma subbands and hhl has been observed. Inters ubband population inversion in simple periodical GaAs/AlAs SLs is presented using X-Gamma resonance. Interband PL measurement and calculation of the o verlap integral between electrons and hole subbands confirm the intersubban d population inversion. Carrier injection into higher subbands using X-Gamm a resonance is expected to be useful for achieving simple quantum cascade l aser structures.