Epitaxial growth of In1−xGaxSb thin films by multitarget rf sputtering

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Abstract
Single‐crystal epitaxial In1−xGaxSb thin films have been grown at compositions ranging from x=0 to x=1 on a variety of substrates including BaF2, NaCl, and InSb using multitarget rf sputtering. The films were deposited on rotating substrates from two targets, InSb and GaSb, with separate discharges allowing independent control of relative sputtering rates. Alloy‐film composition was determined by Auger spectroscopy using bulk standards. The results agreed very well with predicted values calculated from a simple theory which is presented in this paper. Within experimental error, measured lattice constants were found to vary linearly with alloy‐film composition. The amorphous to polycrystalline to single‐crystal growth transition temperatures were found to increase with Ga concentration in the films. Single‐crystal InSb films were obtained at substrate temperatures as low as 150 °C. High dislocation densities were observed in In‐rich films due to large film‐substrate lattice mismatch. Thermoelectric measurements indicated that In‐rich films were n type while Ga‐rich films were p type with the n‐to‐p crossover occurring at approximately In0.58Ga0.42Sb. In addition to homogeneous alloy films, intercalated structures consisting of thin (∼100 Å) alternating layers of InSb/GaSb/InSb... were grown, as well as films which were chemically graded from pure InSb to pure GaSb.

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