Excitonic transition and electronic subband studies in CdxZn1−xTe/ZnTe asymmetric step quantum wells

Abstract

Photoluminescence (PL) and photoluminescence excitation (PLE) measurements were carried out to investigate the interband transitions in CdxZn1−xTe/ZnTe asymmetric step quantum wells which consist of a deep Cd0.1Zn0.9Te well and a shallow Cd0.18Zn0.82Te well bound by two thick ZnTe barriers. The results for the PL data at 20 K showed clearly the excitonic transition from the first electronic state to the first heavy-hole state (E1–HH1), and the PLE data showed the excitonic transition from the second electronic state to the first heavy-hole state (E2–HH1), which in this case is forbidden by the selection rules in contrast to the square-quantum-well case, together with the (E1–HH1) transition. The electronic subband energies and the wave functions in the step quantum wells were calculated, taking into account the strain effects by an envelope-function approximation and the calculated values of the interband transitions were in reasonable agreement with those obtained from the PL and the PLE measurements. These results indicate that CdxZn1−xTe/ZnTe step quantum wells hold promise for potential applications such as new types of modulators and quantum-well infrared photodetectors in the blue-green region of the spectrum.