In this paper we present vertical tunnel diodes and tunnel FETs (TFETs) based on III-V-Si nanowire heterojunctions. We experimentally demonstrate InAs-Si Esaki tunnel diodes with record high currents of 6 MA/cm2 at 0.5 V in reverse bias. Furthermore, we have fabricated vertical InAs-Si nanowire TFETs with gate-all-around architecture and high-k dielectrics. The InAs-Si combination allows achieving high Ion/Ioff ratios above 106, with Ion of 2.4 μA/μm and an inverse subthreshold slope of 150 mV/dec over three decades. The achieved improvements can be attributed to increased nanowire doping and Ni alloying of the top contact. The results indicate the benefits of the InAs-Si material system combining the possibility of achieving high Ion with high I on/Ioff ratio. © 2012 IEEE.