Aluminum-doped n-type ZnTe layers grown by molecular-beam epitaxy

N-type ZnTe layers with high electron concentration are grown by molecular- beam epitaxy using aluminum as the donor species. The ZnTe:Al layers show a high structural quality with a narrow x-ray diffraction linewidth (24 arcs ec) and a high carrier concentration up to n=4x10(18) cm(-3) with low resis tivity (rho =0.017 Omega cm). The dependence of the electron mobility on th e carrier concentration suggests that the dominant scattering mechanisms in the ZnTe:Al layers are ionized impurity scattering and polar optical phono n scattering. The photoluminescence spectrum of moderately doped ZnTe layer s shows strong Al-donor-related bound exciton lines: I-2 (2.378 eV) and don or-acceptor pair emission (zero phonon energy=2.324 eV) with a weak deep-le vel emission (2.19 eV). Highly Al-doped layers show an increase in the deep -level emission intensity and a decrease in carrier mobility, which are int erpreted in terms of the increase in the carrier compensation. (C) 2001 Ame rican Institute of Physics.