Effect of bismuth impurity on carrier density in PbSe : Bi : Se epitaxial layers

The dependence of the Hall carrier density on bismuth concentration, n, p = f(N-Bi), in PbSe:Bi:Se/BaF2 films has been studied. The films were grown b y vacuum condensation from two independent molecular beams (PbSe:Bi and Se- 2) mixed directly at the surface of a (111)BaF2 substrate heated to 350 deg reesC. The bismuth concentration in the stock was 0-0.3 at. %. Two specific portions can be distinguished in the experimental n, p = f(N-Bi) dependenc e. At N-Bi > 0.0375 at. %, the electron density is close to N-Bi; at low bi smuth concentrations, N-Bi < 0.0375 at. %, the linear run of the n = f(N-Bi ) dependence is violated, and the conduction changes to p-type. All the dop ed films under study are saturated with selenium. This is a necessary condi tion for obtaining the highest electron densities in the films at N-Bi corr esponding to the linear portion of the n = f(N-Bi) dependence. The results are discussed in terms of a thermodynamic model of the impurity interaction with intrinsic defects in PbSe, taking into account the amphoteric behavio r of bismuth atoms in lead selenide. (C) 2001 MAIK "Nauka/Interperiodica".