Axial pn-junctions formed by MOVPE using DEZn and TESn in vapor–liquid–solid grown GaAs nanowires

We report on axial pn-junctions in GaAs nanowires. The nanowires were grown by MOVPE on (111)B GaAs substrates using the vapor–liquid–solid mechanism in combination with Au seed particles. At the low growth temperature of 400°C any additional growth on the nanowire sidewalls can be excluded such that a pure axial pn-junction is realized. p-Type doping was provided by diethyl zinc, while tetraethyl tin was introduced for n-type doping. The impact of dopant supply was investigated both on structural properties and on carrier density. The carrier type was independently verified by processed nanowire metal–insulator FETs. The lengths of the whole pn-GaAs nanowires reach up to 20μm while their diameters are up to a few 100nm, as defined by the Au seed particles used. The pn-GaAs nanowire device exhibits diode-like I–V characteristics and strong electroluminescence. While the reverse current is in the low pA-regime, the forward current reaches a few μA, limited by the n-doped side. A diffusion voltage VD=1.4V is determined, which corresponds to the GaAs band gap energy. To our knowledge this is the first axial GaAs pn-diode realized in a single GaAs nanowire.