Atomic Hydrogen Assisted Growth of Si-Ge Heterostructures on (001) Si

Abstract

AbstractA study of the interface chemical and physical abruptness of Si-Ge heterostructures grown on (001) Si by molecular beam epitaxy under atomic hydrogen exposure is reported. Atomic hydrogen (AH) was produced by the dissociation of molecular hydrogen interacting with a hot tungsten filament. Secondary-ion mass spectroscopy (SIMS) of structures made of alternating Ge (0.5 nm)/Si (40 nm) layers demonstrated that AH can effectively suppress Ge surface segregation. The segregation length was reduced from 1.5 nm to about 0.5 nm in films grown at a hydrogen partial pressure of −5 × 10-3 Pa and cell temperature of 2140 °C with an estimated cracking efficiency of ~5%. However, the high hydrogen background pressure had detrimental effects on the physical sharpness of the interfaces. This was evidenced by comparing the interface quality of Si/Ge atomic layer superlattices grown with and without AH exposure. X-ray reflectivity and Raman spectroscopy revealed a significant increase of the interface roughness, although the periodic character and the good crystallinity of the structures were preserved.