Hydrogen in amorphous Si and Ge during solid phase epitaxy

Studies into the effect of hydrogen on the kinetics of solid phase epitaxy (SPE) in amorphous Si (a-Si) and Ge (a-Ge) are presented During SPE, H diffuses into Surface amorphous layers from the surface and segregates at the crystalline-amorphous interface Some of the H crosses the interface and diffuses into the crystalline material where it either leaves the sample or is trapped by defects H segregation at concentrations Lip to 2 3 x 10(20)H/cm(3) is observed in buried pha-Si layers with the SPE rate decreasing by up to 20% H also results in a reduction of dopant-enhanced SPE rates and is used to explain the asymmetry effects between the SPE velocity profile and the dopant concentration profile observed with shallow dopant implants. Conversely. H diffusion is enhanced by dopants in a-Si These studies suggest that H diffusion and SPE may be mediated by the same defect. The extent of H in-diffusion into a-Ge surface layers during SPE is about one order of magnitude less that that observed for a-Si layers This IS thought to be due to the lack of a stable surface oxide on a-Ge However, a considerably greater retarding effect on the SPE rate in a-Cc of up to 70% is observed A single unifying model is applied to both dopant-enhanced SPE and H diffusion processes (C) 2009 Elsevier B.V. All rights reserved.