Thin germanium-carbon alloy layers grown directly on silicon for metal-oxide-semiconductor device applications

We report the growth and characterization of thin (≪35 nm) germanium-carbon alloy (Ge_1-xC_x) layers grown directly on Si by ultrahigh-vacuum chemical vapor deposition, with capacitance-voltage and leakage characteristics of the first high-κ/metal gate metal-oxide-semiconductor (MOS) capacitors fabricated on Ge_1-xC_x. The Ge_1-xC_x layers have an average C concentration of approximately 1 at. % and were obtained using the reaction of CH₃GeH₃ and GeH₄ at a deposition pressure of 5 mTorr and growth temperature of 450 °C. The Ge_1-xC_x films were characterized by secondary ion mass spectrometry, atomic force microscopy, x-ray diffraction, and cross-sectional transmission electron microscopy. A modified etch pit technique was used to calculate the threading dislocation density. The x-ray diffraction results showed that the Ge_1-xC_x layers were partially relaxed. The fabricated MOS capacitors exhibited well-behaved electrical characteristics, demonstrating the feasibility of Ge_1-xC_x layers on Si for future high-carrier-mobility MOS devices.