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 (similar to 1.35 e V) of conduction band edges. Even though donors in ZnTe create deep levels, we have successfully made two-dimensional electron gases in this system th rough modulation doping of a CdSe layer sandwiched between n-doped (chlorin e) ZnTe layers. In addition, we have fabricated ''magnetic'' two-dimensiona l electron gases, where a small amount of Mn is included in the CdSe quantu m well, with the aim of studying spin-dependent phenomena in reduced dimens ions. We find efficient transfer of electrons into the (Cd, Mn)Se quantum w ell, even when the doping layer is separated from the well by up to 150 nm of intrinsic ZnTe. By utilizing narrow spacer layers, carrier concentration s of up to 2 x 10(13) cm(-2) are demonstrated. Low temperature magnetotrans port measurements of nonmagnetic samples indicate a Hall mobility typically in the range 5000-10000 cm(2)/Vs, but somewhat lower quantum mobilities (s imilar to 3000 cm(2)/V s). In the magnetic samples, while both the carrier concentrations and the Hall mobility are relatively unaffected by the prese nce of the Mn ions, a dramatic decrease in the quantum mobility is observed . (C) 1999 American Vacuum Society. [S0734-211X(99)07003-1].