Strain-Induced Effects on Band-to-Band Tunneling and Trap-Assisted Tunneling in Si Examined by Experiment and Theory

Strain is commonly used in metal–oxide–semiconductor technologies to boost on-state performance. This booster has been in production for at least a decade. Despite this, a systematic study of the impact of strain on off-state leakage current has been lacking. Herein, experimental data and ab initio calculations are used to refine existing models to account for the impact of strain on band-to-band tunneling and trap-assisted tunneling in silicon. It is observed that the strain may dramatically increase the leakage current, depending on the type of tunneling involved. For band-to-band and trap-assisted tunneling, low uniaxial strains of 0.1% (or 180 MPa) can increase the leakage current by 60% and 10% compared to the unstrained case, respectively. Using models, it is predicted that compressive strain on the order of 1% (or 2 GPa) can increase the leakage current by 150 times. Conversely, tensile strain may diminish or at most double the leakage current in all observed cases. Though detrimental in conventional inversion-mode metal-oxide-semiconductor field-effect-transistor, these processes may be used to boost the performance of tunnel field-effect transistors, where on-state current is defined by band-to-band tunneling.