Photoluminescence kinetics of multiperiod GaAs/AlGaAs structures with asymmetric barriers promising for making unipolar lasers

Photoluminescence kinetics in multiperiod GaAs/AlGaAs quantum-well structures with asymmetric barrier heights has been investigated. Owing to the barrier asymmetry, a time constant of nonradiative recombination between the laser subbands of $9$ ps has been achieved, which is record long for unipolar lasers and exceeds the nonradiative relaxation time constant of the lower laser subband. This provides population inversion in the system. Efficient suppression of an unwanted cascade transition between the laser subbands via quasi-continuum states has been demonstrated.