Electrical and optical properties of phosphorus doped Ge sub(1-y)C sub(y)

• Published in: Thin solid films Vol. 321; pp. 47 - 50
• Main Authors: Dashiell, M W, Troeger, R T, Roe, K J, Khan, A-S, Orner, B, Olowolafe, J O, Berger, P R, Wilson, R G, Kolodzey, J
• Format: Journal Article
• Language: English
• Published: 26.05.1998
• ISSN: 0040-6090

In situ n-type doping was investigated for Ge sub(1-y)C sub(y)/Si heteroepitaxial layers (y to approximately 0.001) for a potential optoelectronic material compatible with Si. Using a solid GaP sublimation source for phosphorus doping, epitaxial Ge sub(1-y)C sub(y) films were in situ doped on Si(100) substrates during solid source molecular beam epitaxy and we compare their electrical and optical properties with those of epitaxial Ge on Si. Infrared absorption revealed red shifts in the absorption of visible light with increasing P doping for both Ge sub(1-y)C sub(y) and Ge. The index of refraction decreases for Ge sub(1-y)C sub(y) layers compared with Ge. Free carrier absorption increased with increasing phosphorus concentrations, following a wavelength dependence of approximately lambda super(3.1) in the region of 10-20 mu m for heavily doped material. Addition of C did not affect the incorporation of P donors in the grown layers or the electrical activation of the donors. An increase in the electron mobility for heteroepitaxial Ge sub(1-y)C sub(y) layers compared with Ge was observed for the doping levels studied.