Off-State Leakage Induced by Band-to-Band Tunneling and Floating-Body Bipolar Effect in InGaAs Quantum-Well MOSFETs

The physics of off-state drain leakage (I
_off
) in scaled self-aligned InGaAs quantum-well (QW) MOSFETs is investigated through experiments and simulations. Excess I
_off
is observed in InGaAs QW-MOSFETs with very short contact-to-channel spacing. This current bears the marks of band-to-band tunneling (BTBT) that takes place at the drain edge of the channel. However, a pure BTBT current does not explain the observed magnitude of I
_off
nor its gate length dependence. For this, we invoke floating-body bipolar amplification of the BTBT current in the QW channel. Device simulations that include BTBT and drift diffusion are consistent with the magnitude of the experimental I
_off
and its gate length scaling behavior. The understanding derived here suggests a number of paths to mitigate BTBT-induced off-state current in scaled InGaAs QW-MOSFETs.