Next generation of Ge_(1-y)Sn_(y) (y velence 0.01-0.09) alloys grown on Si(100) via Ge_(3)H_(8) and SnD_(4): Reaction kinetics and tunable emission

摘要

Film growth and reaction kinetics studies have shown that trigermane (Ge_(3)H_(8)) is a superior Ge source for the epitaxial synthesis of Ge_(1-y)Sn_(y)/Si(100) alloys using ultra-high vacuum chemical vapor deposition. The Ge_(3)H_(8)/SnD_(4) combination yields 3-4 times higher growth rates than the traditional Ge_(2)H_(6)/SnD_(4) approach, with film Sn/Ge ratios reflecting the corresponding gas-phase stoichiometries much more closely. These advances have led to optical quality Ge_(1-y)Sn_(y) layers with Sn concentrations up to at least 9percent and thicknesses approaching 1 (mu)m. These thick films are found to be crucial for the observation of a strong, tunable photoluminescence signal near the threshold of the predicted direct-indirect bandgap crossover.