GROWTH AND ELECTRICAL-PROPERTIES OF SPUTTER-DEPOSITED SINGLE-CRYSTAL GASB FILMS ON GAAS SUBSTRATES

Single-crystal GaSb films have been grown on semi-insulating (100) GaAs substrates using multitarget sputtering to vary the Sb/Ga atomic flux ratio r impinging on the growing film. The effects of systematic variations in growth variables (r, growth temperature, target voltage, and Ar sputtering gas pressure and purity) on the electrical properties of deposited films were evaluated. Temperature-dependent (8-600 °K) Hall coefficient and resistivity measurements were carried out on all films in order to determine the concentration and ionization energies of impurity and point-defect levels. In all cases the Hall-coefficient measurements could be fitted with two acceptor levels and a net concentration of very shallow (<1 meV) acceptors. The deepest acceptor level occurred at 80 meV above the valence-band edge and was associated with electrically active sites on dislocations originating at the film-substrate interface. A second acceptor level occurred at 40 meV above the valence-band edge and was directly related to Sb vacancies or equivalent point-defect complexes. The net concentration of very shallow acceptors was related to both Sb vacancies and donor impurities, probably oxygen. The room-temperature hole-carrier concentration in these films ranged from 5×1015 to 1×1018 cm-3, while the hole mobility was between 1 and 100 cm2/V sec. Analysis of temperature-dependent mobility data showed that the dominant charge-carrier scattering sites were dislocations introduced due to the large film-substrate lattice mismatch, ∼8%.