Electroreflection from higher subband transitions in a ZnSe–Zn 0.8Cd 0.2Se superlattice

Abstract

Electroreflection spectra have been measured to investigate the electric field effects on excitonic modulation for several subbands in a ZnSe–Zn 0.8Cd 0.2Se superlattice structure. In photoluminescence spectra, three subbands originating from the n=1 heavy-hole ( E 1hh), n=2 heavy-hole ( E 2hh) and light-hole ( E 2lh) excitonic peaks were observed at 17 K. In a weak electric field of only 3.5 kV/cm the induced excitonic transitions corresponding to the above three peaks were all clearly modulated both at 77 K and at room temperature. The polarization dependence of the excitonic transition in ZnSe–Zn 0.8Cd 0.2Se superlattices was studied by low-field electroreflection spectroscopy. A new peak observed in the lower energy side of the n=2 heavy-hole exciton E 2hh at room temperature is attributed to the forbidden transition in zero field from the n=2 heavy-hole state to the n=1 electron state ( E 2h,1e). This reflection change is found to be polarization dependent.