Vacancy Doping of GaAs

GaAs epitaxial films are deposited on GaAs and Ge substrates. The simple and cost-effecteive close-spaced vapor transport technique is used. Since the mean free path of the reactive species in this system is larger than the separation between source and substrate, the reaction is mainly contlled by the displacement of the chemical equilibrium constant corresponding to the souree and substrate temperatures. The analysis of the electrical transport data of the epitaxial layers deposited on SI GaAs indicate that the reported phase extent of the compound might be of major importance in determining the electrical behaviour of the crystals, especially in the case of the so-called “undiped” SI GaAs. The examination of the reaction mechanisms shows that the films are grown under arsenic-rich conditions. This results in the formation of gallium vacancies. These can be partially filled by arsenic atoms introducing EL2 antisite complexes. This phase extent related phenomenon gives rise to the formation of a divalent deep lying donor level and a shallow monovalent donor state. In addition, the remaining unoccupied gallium vacancies are assumed to be responsible for the introduction of a deep lying acceptor level. It is argued by way of the Shockley multilevel for the introduction of a deep lying acceptor level. It is argued by way of the Shockley multilevel impurities analysis that these vacancies are the compensating species responsible for the formation of “undoped” or “vacancy doped” SI GaAs grown under arsenic-rich conditions.