Growth of single-crystal metastable InSb1−xBix and (GaSb)1−xGex semiconducting films

Abstract

Epitaxial metastable InSb1-xBix alloys with InBi concentrations up to 12 mol % and (GaSb)1−xGex alloys with compositions across the pseudobinary phase diagram have been grown on GaAs substrates by multitarget rf sputtering. The InSb1−xBix film were n-type while the (GaSb)1−xGex films were p-type. Polycrystalline films from both alloy systems grown on Corning 7059 glass substrates exhibited strong (220) preferred orientation with lattice constants obeying Vegard’s law. Annealing experiments showed that the InSb1−xBix films were metastable in two directions on the In–Sb–Bi ternary phase diagram—the solid solubility of tetragonal InBi in zinc blende structure InBi was increased by more than a factor of 4 and the width of the InSb–InBi pseudobinary ’’line compound’’ phase field was increased to ?0.5%. Both InSb1−xBix and (GaSb)1−xGex films were found to be stable to decomposition during long anneals which, in the case of InSb1−xBix, were within 100°C of the equilibrium liquidus temperature. Annealing studies carried out on (GaSb)0.38Ge0.62 showed that such films transform from the as-deposited (220) oriented alloy to GaSb–rich and Ge–rich phases in which the solute concentrations continuously decrease until an equilibrium two phase alloy is obtained. The activation energy for this process is 3.1 eV.