Fabrication of p-MOSFETs on germanium epitaxially grown on gallium arsenide substrate by chemical vapor deposition

We demonstrate a p-MOSFET fabricated on Ge/GaAs heterostructure. The Ge layer was epitaxially grown on GaAs substrate by high vacuum chemical vapor deposition. High-quality single crystalline Ge film confirmed by X-ray diffraction and transmission electron microscopy was achieved with a very low root-mean-square roughness of 5 angstrom measured by atomic force microscopy. Secondary ion mass spectrometry results indicate that no Ga and As out-diffusion to Ge epi layer can be observed. By employing silane passivation, Ge p-MOSFET with TaN/HfO2 gate stack was fabricated on Ge/GaAs heterostructure. The resultant transistor exhibited excellent subthreshold swing of 86 mV/dec and 1(on)/1(off) ratio greater than four orders. Additionally, similar to 1.7 times hole mobility enhancement over the universal curve of Si was achieved. (c) 2007 The Electrochemical Society.