Fabrication and characterization of a two-dimensional electron gas in modulation doped ZnTe/Cd1−xMnxSe quantum wells

The II–VI semiconductors ZnTe and CdSe are nearly lattice-matched materials which have a type-II band alignment with a large offset (∼1.35 eV) of conduction band edges. Even though donors in ZnTe create deep levels, we have successfully made two-dimensional electron gases in this system through modulation doping of a CdSe layer sandwiched between n-doped (chlorine) ZnTe layers. In addition, we have fabricated “magnetic” two-dimensional electron gases, where a small amount of Mn is included in the CdSe quantum well, with the aim of studying spin-dependent phenomena in reduced dimensions. We find efficient transfer of electrons into the (Cd, Mn)Se quantum well, even when the doping layer is separated from the well by up to 150 nm of intrinsic ZnTe. By utilizing narrow spacer layers, carrier concentrations of up to 2×1013 cm−2 are demonstrated. Low temperature magnetotransport measurements of nonmagnetic samples indicate a Hall mobility typically in the range 5000–10 000 cm2/V s, but somewhat lower quantum mobilities (∼3000 cm2/V s). In the magnetic samples, while both the carrier concentrations and the Hall mobility are relatively unaffected by the presence of the Mn ions, a dramatic decrease in the quantum mobility is observed.