Bandgap dependence of band-to-band tunneling and defect-mediated excess currents in SiGe/Si heterojunction tunnel diodes grown by RTCVD

There is great interest in SiGe/Si heterojunction tunnel diodes for novel devices such as sharp subthreshold slope MOSFET\´s. High tunneling current densities are a clear goal (for MOSFET drive current, e.g.). This work presents two clear results: (i) a direct measurement of the dependences on bandgap (Ge fraction) of the direct tunneling current vs. the "excess" defect-assisted tunneling current, and (ii) the highest direct tunneling currents (NDR current peaks) observed in Si-based heterojunction diodes grown by chemical vapor deposition. In summary, we have shown SiGe/Si tunnel diodes with high peak current density and a clear trend of more dominant band-to-band tunneling over excess current as bandgap is reduced.