Investigation of electric-field-dependent population properties in a GaAs/(Al,Ga)As multiple, asymmetric double quantum well structure by photoluminescence spectroscopy

Photoluminescence (PL) spectroscopy is used to study the population properties of a multiple, asymmetric GaAs/(Al,Ga)As double quantum well superlattice, which represents a simplified version of the active region of a quantum cascade laser (QCL). In the case of anti-Stokes PL of the narrower well, which is observed for excitation between the excitonic states of the two quantum wells and sufficiently high electric field strengths, the photocarriers are only excited in one of the two wells. The anti-Stokes signal gives direct evidence for transport of electrons and holes through the (Al,Ga)As barriers. An analysis of the electric-field dependence of the conventional PL as well as the anti-Stokes PL signal demonstrates that the population of the subbands can be determined in the limit of weak excitation intensity.