Electrothermal characteristics of strained-Si MOSFETs in high-current operation

The electrothermal characteristics of strained-Si MOSFETs, operating in the high-current regime, have been studied using device simulation. The phonon mean-free-path of strained-Si devices in the presence of high electric fields is determined, based on fullband Monte Carlo device simulation. Strained-Si nMOS devices have higher bipolar current gain and impact ionization rates compared to bulk-Si nMOS devices due to the smaller energy bandgap and longer phonon mean-free-path. Even though strained-Si devices have self-heating problems due to the lower thermal conductivity of the buried SiGe layer, the devices can be used beneficially for electrostatic discharge protection devices to achieve lower holding voltage (V_h) and higher second breakdown triggering current (I_t2), compared to those of bulk-Si devices, owing to the high bipolar current gain and current uniformity.