OPTICAL STUDY OF VERTICAL TRANSPORT IN CD0.82MN0.18TE/CDTE SUPERLATTICES

We have performed cw and time-resolved photoluminescence measurements on a 30/30 Cd0.82Mn0.18Te/CdTe superlattice containing two enlarged wells with different widths, namely, 60 and 200 angstrom. The distance between the two enlarged wells is 2400 angstrom and the wider one is located 0.96 mum away from the sample surface. Excitation above the alloy band gap allows us to study the Bloch transport along the growth direction of the superlattice. Both ambipolar transport and hopping of carriers are observed. Mobilities of the order of 4 X 10(4) cm2/V s and 3 X 10(2) cm2/V s are estimated for the two processes, respectively, at low temperatures (< 20 K). Transfer of excitation between the two wells is also observed when exciting resonantly the thinner enlarged well, i.e., below the superlattice band gap. This transfer is assigned to carrier hopping on localized states of the superlattice.