Excess Off-State Current in InGaAs FinFETs

Abstract

We present a detailed study of the off-state leakage current in scaled self-aligned InGaAs FinFETs. In long-channel devices, band-to-band tunneling at the drain-end of the channel is shown to be the root cause of excessive off-state current. This conclusion emerges from its characteristic electric field and temperature behavior and the absence of gate length and fin width dependencies. In short-channel devices, off-state current is significantly larger and it increases as the gate length shortens or the fin widens. We attribute this behavior to current multiplication through the gain of a floating-base parasitic bipolar transistor that is present inside the MOSFET. We extract the bipolar current gain which in short-channel devices is found to increase as the gate length shortens and decrease as the fin width narrows. In long channel devices, the current gain drops exponentially due to base recombination. This has allowed us to extract the diffusion length of electrons in the body of the transistor.