Direct Determination of Minority Carrier Diffusion Lengths at Axial GaAs Nanowire p–n Junctions

Abstract

Axial GaAs nanowire p-n diodes, possibly one of the core elements of future nanowire solar cells and light emitters, were grown via the Au-assisted vapor-liquid-solid mode, contacted by electron beam lithography, and investigated using electron beam induced current measurements. The minority carrier diffusion lengths and dynamics of both, electrons and holes, were determined directly at the vicinity of the p-n junction. The generated photocurrent shows an exponential decay on both sides of the junction and the extracted diffusion lengths are about 1 order of magnitude lower compared to bulk material due to surface recombination. Moreover, the observed strong diameter-dependence is well in line with the surface-to-volume ratio of semiconductor nanowires. Estimating the surface recombination velocities clearly indicates a nonabrupt p-n junction, which is in essential agreement with the model of delayed dopant incorporation in the Au-assisted vapor-liquid-solid mechanism. Surface passivation using ammonium sulfide effectively reduces the surface recombination and thus leads to higher minority carrier diffusion lengths.

Core–shell InGaN/GaN nanowire light emitting diodes analyzed by electron beam induced current microscopy and cathodoluminescence mapping

“…[8][9][10][11][12][13][14] In particular, EBIC microscopy is a perfectly dedicated tool to investigate the structural and the electrical properties of the three-dimensional nanostructured LEDs. In the past years, several EBIC investigations of single nanowires and nanowire devices built of different materials have been reported, [15][16][17][18][19][20] sometimes coupled with cathodoluminescence (CL) mapping. 9 Regarding nitride nanowires, in our previous work we have addressed the parallel transport properties of core-shell InGaN/GaN single wire LEDs.…”

Direct Imaging of p–n Junction in Core–Shell GaN Wires

“…1 Along with a careful axial and/ or radial design of doping levels and (alloy) compositions at the single wire level, an increased versatility is offered by wire devices as compared to planar layer devices. 1,6−11 The p−n junctions in wires with either axial [4][5][6]11 or core− shell [8][9][10]12,13 geometry have been reported to provide the building block of optoelectronic applications. The latter geometry leads to a three-dimensional (3D) core−shell p−n junction thanks to a shell generally deposited on both the sidewalls and the top of the core.…”

Electrical, structural, and optical properties of sulfurized Sn-doped In2O3 nanowires

“…For instance the surface modification of III-V NWs such as InAs and GaAs NWs using sulfur has been shown to improve their electrical and optical properties [2][3][4][5][6], but the effect of sulfur on the structural, electrical and optical properties of metal oxide (MO) NWs has not been considered previously, despite the fact that it leads to a suppression of surface recombination and improvement of the photoluminescence (PL) in bulk ZnO [7,8]. Controlling the surface properties of MO NWs is also necessary in order to suppress the adsorption and desorption of oxygen which is responsible for charge fluctuations and has been achieved so far by using polyimide and polymethyl methacrylate on ZnO and SnO 2 NWs, respectively [9,10].…”