A comparative study on deep levels in p-ZnSe grown by MBE, MOMBE and MOVPE

Abstract

A comparative study on deep levels in p-ZnSe grown by molecular beam epitaxy (MBE), metalorganic MBE (MOMBE), and metalorganic vapor phase epitaxy (MOVPE) has been carried out to elucidate the nature of deep levels. A hole trap level which is located at 0.38 eV above the valence band is inevitably introduced into p-ZnSe by nitrogen doping. The formation of other hole traps is associated with native defects due to non-stoichiometry of ZnSe and depends on growth methods and conditions. Electron traps were also observed in the MOMBE and the MOVPE-grown samples. The absence of the same electron trap levels in the MBE samples indicates that the traps originate from insufficient decomposition of metalorganic source precursors. These findings illustrate the necessity of forming p-ZnSe (1) under stoichiometric conditions, (2) at relatively low temperature to suppress evaporation of Zn and Se, and (3) with well-decomposed metalorganic sources, in order to achieve p-type doping with low degree of compensation by hole and electron traps.