Experimental and TCAD Investigation of the Two Components of the Impact Ionization MOSFET (IMOS) Switching

The impact ionization MOSFET is a new device witch enables subthreshold slopes down to a few mV/dec. It uses impact ionization to switch from the off-state to the on-state. In the literature, the avalanche is said to be always initiated near the gate edge. In this letter, we report for the first time a new way to initiate the avalanche breakdown, namely near the source junction. Technology computer-aided design simulations enable us to analyze this new mechanism and highlight the parameters allowing switching from the ldquosource junctionrdquo mode to the ldquogate mode.rdquo Experimental investigations are then performed in order to correlate the simulations with electrical measurements. In particular, we show that the subthreshold slope does not depend on the gate length in the source junction mode unlike in the gate mode.