Growth of single crystal GaAs and metastable (GaSb) 1− xGe xAlloys by sputter deposition: Ion-surface interaction effects

Abstract

High quality single crystal GaAs films and metastable (GaSb) 1- x Ge x alloys have been grown on (100) GaAs substrates by sputter deposition. Low energy ion bombardment of the growing films was used to control elemental incorporation probabilities and hence doping concentrations in the case of the GaAs films and was an essential feature in allowing the growth of the metastable alloys. The results in both cases are discussed in terms of the operative mechanisms including trapping processes, preferential sputtering, surface segregation, and collisional mixing. Unintentionally doped GaAs films were high resistivity 10 5-10 6 Ω cm n-type with room temperature mobilities as high as 5000 cm 2/V·s. Multitarget rf sputtering was used to grow epitaxial metastable p-type (GaSb) 1- x Ge x alloys with compositions across the pseudobinary phase diagram. The maximum growth temperature ranged from 490 to 520°C depending on the alloy composition and annealing experiments indicated that the films exhibit good high temperature stability. While the free energy difference between the single phase metastable and the two phase equilibrium states is on the order of 20 meV/atom, the measured activation barrier for the transformation is ≈3 eV.