ELECTRICAL AND OPTICAL-PROPERTIES OF PHOSPHORUS-DOPED GE1-YCY

In situ n-type doping was investigated for Ge1-yCy/Si heteroepitaxial layers (y-0.001) for a potential optoelectronic material compatible wi th Si. Using a solid GaP sublimation source for phosphorus doping, epi taxial Ge1-yCy films were in situ doped on Si(100) substrates during s olid source molecular beam epitaxy and we compare their electrical and optical properties with those of epitaxial Ge on Si. Infrared absorpt ion revealed red shifts in the absorption of visible light with increa sing P doping for both Ge1-yCy and Ge. The index of refraction decreas es for Ge1-yCy layers compared with Ge. Free carrier absorption increa sed with increasing phosphorus concentrations, following a wavelength dependence of similar to lambda(3.1) in the region of 10-20 mu m for h eavily doped material. Addition of C did not affect the incorporation of P donors in the grown layers or the electrical activation of the do nors. An increase in the electron mobility for heteroepitaxial Ge1-yCy layers compared with Ge was observed for the doping levels studied. ( C) 1998 Elsevier Science S.A. All rights reserved.