Size, composition, and doping effects on In(Ga)As nanowire/Si tunnel diodes probed by conductive atomic force microscopy

We investigate the effect of various parameters on the room-temperature interband tunneling characteristics of molecular beam epitaxy grown, intrinsically n-type In(Ga)As nanowires (NWs) on p-type silicon (Si) substrate using conductive atomic force microscopy. Large interband tunnel currents (>40 kA/cm2) and reduced breakdown voltages are obtained by increasing the p-type substrate doping level to >1 1019 cm-3. Current mapping under forward bias reveals a bimodal distribution of NW/Si hetero-junction tunnel diodes exhibiting either negative differential resistance (NDR, Esaki diode) or high excess currents (without NDR). By downscaling the NW diameter from similar to 90 nm to similar to 25 nm, peak-to-valley current ratios in NDR-type diodes increase and saturate with maximum values of similar to 3. Increasing Ga content (xGa up to similar to 0.1) in In-rich ternary InGaAs NWs preserves the NDR behavior, while the peak current shifts to lower voltages due to reduced Fermi energy in InGaAs. Band profile calculations were performed to further support these findings.