Growth and phase stability of epitaxial metastable InSb1−xBix films on GaAs. I. Crystal growth

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Epitaxial metastable InSb1−xBix films with InBi concentrations up to 12 mole % have been grown on (110) GaAs substrates by multitarget rf sputtering. Tetragonal InBi is a semimetal whose equilibrium solid solubility in zinc blende structure InSb is 2.6 mole %. Low-energy ion bombardment of the growing film was used to modify the elemental Sb and Bi incorporation probabilities σSb and σBi through preferential resputtering in order to maintain overall stoichiometry and to allow the growth of single-crystal extended solid solution alloys at elevated temperatures. The effects of the Bi to Sb impingement flux ratio JBi/JSb, film growth temperature TS, and the Ar sputtering pressure PAr on the composition and structure of the as-deposited films as well as their metastable solid solubility, were also investigated. Holding all growth variables except one constant in a given set of experiments, the ratio σBi/σSb was found to decrease with increasing JBi/JSb, increasing TS, and decreasing PAr . The metastable solid solubility limit increased with decreasing PAr . Single-phase metastable films were n-type semiconductors with the 100 °K carrier concentration increasing from 1.8×1017 to 4.5×1017 cm−3 as the mole % of InBi was increased from 3 to 12. Electron mobilities at this temperature ranged from a few hundred to ∼1000 cm2/V sec. The mobility increased with increasing temperature yielding an activation energy of 0.02 eV. The optical band gap decreased with increasing InBi concentrations indicating a semiconductor-semimetal transition at ∼11 mole % InBi at 20 °K.