Heat generation approximation in modulation-doped field-effect transistors by the energy relaxation between carriers and phonons

A combination of the nonlinear charge-control model, rate balance equations, and electron-phonon scattering is used to simulate the hot-electron transport and heat generation problem of modulation-doped field-effect transistors. Based on the present model, the trend of high-field transport can be well demonstrated. In addition, the heat generation inside the channel can also be estimated by the energy flux balance equation with the energy relaxation rate formulated by polar-optical phonon scattering mechanism. Scaling down the gate length to submicron range, more heat power is generated inside the channel. However, the heat generation ratio reveals that hot electrons carry over half of the energy density gained from the applied electric field directly into drain region. For 0.1 μm gate length, more than 90% energy density is achieved. By reducing the gate length into the deep submicron range, the thermal impact on the drain side becomes more serious and complicated than the one found inside the channel.