Fabrication and Analysis of a ${\rm Si}/{\rm Si}_{0.55}{\rm Ge}_{0.45}$ Heterojunction Line Tunnel FET

This paper presents a new integration scheme to fabricate a Si/Si_0.55Ge_0.45 heterojunction line tunnel field effect transistor (TFET). The device shows an increase in tunneling current with gate length. The 1- μm gate length device shows on current in excess of 20 μA/μm at VGS=VDS=1.2 V. Low-temperature measurements, performed to suppress trap-assisted tunneling (TAT), reveal the point subthreshold swing as low as 22 mV/dec at 78 K. Field-induced quantum confinement effects are found to increase the tunneling onset voltage by ~ 0.35 V. Variation of the tunneling onset voltage measured experimentally is correlated to variation in the pocket thickness and its doping concentration. Small geometry devices were found to be more susceptible to microvariations in the pocket thickness and doping concentration.