Characterization of n-type Ge layers on Si (100) substrates grown by rapid thermal chemical vapor deposition

Phosphorus-doped n-type Ge layers were grown on p-type Si (100) wafers (8 in. in diameter, resistivity 5-15 Ω cm) using rapid thermal chemical vapor deposition (RTCVD). The surface morphology was very smooth, with a root mean square (RMS) surface roughness of 0.29 nm. The in-plane lattice constant calculated from high-resolution X-ray diffraction (HR-XRD) data was 0.5664 nm, corresponding to in-plane tensile strain of ∼0.47%. The Raman Ge peak for each location indicates tensile strain from the Ge wafer. We estimated the in-plane strain as tensile strain of ∼0.45%, in excellent agreement with the XRD analysis. Initial photocurrent spectrum experiments on the sample confirm valence band splitting of the direct gap induced by tensile strain. The temperature dependence of the direct bandgap energy EΓ1 of Ge can be described by the empirical Varshni expression EΓ1(T)=0.864-5.49×10-4T2/(T+296).