Substitutional C effect on generation lifetime in MBE-grown SiGeC layers

Abstract

This paper investigates the effect of substitutional carbon on generation lifetime in pseudomorphically strained Si 1−x−y Ge x C y (x ∼ 0.1, y < 0.006) layers grown by gas source molecular beam epitaxy (GSMBE). The electrical assessment consists of capacitance-voltage and capacitance transient techniques on metal-oxide-semiconductor (MOS) capacitors based on Si/SiGeC heterostructures. The carrier lifetime study shows microsecond range lifetimes for substitutional carbon contents, [C s ] < 0.5%. The charge confinement in the potential well, formed at the SiGeC/Si heterointerface, is found to have less effect on generation lifetime than the substitutional to interstitial carbon ratio in these alloys. Samples with substitutional carbon concentrations above 0.5% exhibit a sharp decrease of generation lifetime into the nanosecond range, attributed to an increased ratio of interstitial carbon. Si 0.8826 Ge 0.116 C 0.0014 and Si 0.8809 Ge 0.116 C 0.0031 layers grown by GSMBE can be used in high-performance heterojunction bipolar transistors (HBTs).