Synthesis of Group-IV ternary and binary semiconductors using epitaxy of GeH₃Cl and SnH₄

Ge₁-ₗ-ₘSiₗSnₘ alloys were grown on Ge buffer layers at ultra-low temperature using reactions of SnH₄ and GeH₃Cl for the first time. The latter is a newly introduced CVD source designed for epitaxial development of group IV semiconductors under low thermal budgets and CMOS compatible conditions. The Ge₁-ₗ-ₘSiₗSnₘ films were produced between 160-200oC with 3-5% Si and ~ 5-11 % Sn, which traverses the indirect to direct gap transition in Ge-Sn materials. The films were fully strained to Ge and exhibited defect-free microstructures, flat surfaces, homogeneous compositions, uniform thicknesses and sharp interfaces as required for device manufacturing. A comparative study was then conducted to investigate the applicability of GeH₃Cl for the synthesis of Ge₁-ₘSnₘ binaries under similar experimental conditions. The Ge₁-ₘSnₘ films were grown fully strained to Ge, but with reduced Sn compositions ranging from ~ 2 - 7 % and lower thicknesses relative to Ge₁-ₗ-ₘSiₗSnₘ. This prompted efforts to further investigate the growth behavior of Ge₁-ₘSnₘ using the GeH₃Cl method, bypassing the Ge buffer to produce samples directly on Si, with the aim of exploring how to manage interface strain. In this case the Ge₁-ₘSnₘ on Si films exhibited compositions and thicknesses comparable to Ge₁-ₘSnₘ-on-Ge films; however, their strain states were mostly relaxed, presumably due to the large misfit between Ge₁-ₘSnₘ and Si. Efforts to increase the concentration and thickness of these samples resulted in non-homogeneous multi-phase materials containing large amounts of interstitial Sn impurities.