Toward Nanowire HBT: Reverse Current Reduction in Coaxial GaAs/InGaP n(i)p and n(i)pn Core-Multishell Nanowires

In this work the reduction of reverse currents in Au-catalyzed, MOVPE grown coaxial GaAs nanowire diodes are reported. The reduction is achieved by introducing an interstitial, lattice-matched i-InGaP shell (spacer) as tunneling barrier inside the junction, which also functions as a selective etch stop. With increasing spacer thickness, rectification ratios of >1.57 x 10(6) at +/- 1.65 V, ideality factors of 1.3, and dark saturation current densities as low as 20 pA cm(-2) are extracted, which are related to a reduced tunneling probability. Temperature-dependent DC measurements of junctions with thin spacers show a correlation to a simple (trap-assisted) tunneling model. With absolute reverse currents in the pA range down to -3 V bias, the improved diode is implemented as a collector-base junction in a coaxial n(i)pn nanowire structure by growing an additional, outer n-doped InGaP shell as the emitter layer in a nanowire HBT.