HIGH-FIELD ELECTRON-TRANSPORT IN SIGE ALLOY

Electron transport in unstrained Si1-xGex (0 less-than-or-equal-to x less-than-or-equal-to 0.4) alloy is studied in the present work using the Monte Carlo (MC) simulation technique. Electron transport characteristics (drift velocity, impact ionization (II) coefficient, etc.) are evaluated over a wide range of electric fields. It is found that not only low-field mobility but also saturation velocity and impact ionization coefficients are reduced with increasing Ge fraction due to alloy scattering. More importantly, the high-energy (epsilon > 2 eV) electron population is reduced to a much greater extent than the ionization coefficient. Simple analytical expressions for electron low-field mobility, saturation velocity and II coefficient which can be easily implemented in device simulation programs are proposed.