Zero-bias photocurrents in highly-disordered networks of Ge and Si nanowires

Abstract

Semiconducting nanowire (NW) devices have garnered attention in self-powered electronic and optoelectronic applications. This work explores and exhibits, for the first time for visible light, clear evidence of the zero-biased optoelectronic switching in randomly dispersed Ge and Si NW networks. The test bench, on which the NWs were dispersed for optoelectronic characterization, was fabricated using a standard CMOS fabrication process, and utilized metal contacts with dissimilar work functions-Al and Ni. The randomly dispersed NWs respond to light by exhibiting substantial photocurrents and, most remarkably, demonstrate zero-bias photo-switching. The magnitude of the photocurrent is dependent on the NW material, as well as the channel length. The photocurrent in randomly dispersed GeNWs was found to be higher by orders of magnitude compared to SiNWs. In both of these material systems, when the length of the NWs was comparable to the channel length, the currents in sparse NW networks were found to be higher than those in dense NW networks, which can be explained by considering various possible arrangements of NWs in these devices.

Random networks of core-shell-like Cu-Cu2O/CuO nanowires as surface plasmon resonance-enhanced sensors

“…It is worth noting that the existence of this correlation between Cu nanowire density and Raman intensity is not trivial at all. Sparse nanowire networks have been shown to exhibit counter-intuitive electrical conductivity characteristics 35 , and Clayton et al . have recently reported that the SERS spectra of 4-mercaptopyridine was not significantly influenced when the measurement was moved from a single silver nanowire to two crossed wires 36 .…”

Capillarity-Driven Welding of Semiconductor Nanowires for Crystalline and Electrically Ohmic Junctions

“…Flexible meshes of silicon (Si) and germanium (Ge) NWs have been fabricated, − but the structures are electrically inactive or exhibit high resistances and nonlinear current–voltage ( I–V ) curves , as a result of insulating oxide layers or organic capping ligands between the NWs. The formation of electrically active connections between semiconductor NWs grown by a vapor–liquid–solid (VLS) mechanism has been limited to junctions formed either by electrically biasing individual wires, patterning NWs to intersect during the VLS process, − or using a multistep VLS process to create branched nanowires. − These strategies are generally limited to a low number of NWs and interconnection points.…”

“…19 In comparison to metallic NWs, however, semiconductor NWs could offer a wide range of more advanced functionality by encoding field-effect transistors, 20 p−n junctions, 21 and memory bits 22 within the individual NWs of the network. 23 Flexible meshes of silicon (Si) and germanium (Ge) NWs have been fabricated, 24−28 but the structures are electrically inactive or exhibit high resistances and nonlinear current− voltage (I−V) curves 27,28 as a result of insulating oxide layers or organic capping ligands between the NWs. The formation of electrically active connections between semiconductor NWs grown by a vapor−liquid−solid (VLS) mechanism has been limited to junctions formed either by electrically biasing individual wires, 29 patterning NWs to intersect during the VLS process, 30−32 or using a multistep VLS process to create branched nanowires.…”

Functional Devices from Bottom-Up Silicon Nanowires: A Review

“…Generally, semiconducting nanonets—in comparison with metallic ones—are much less studied and, most of the time, when dealing with NWs, the reported work is an isolated study that is not followed by any other publication [ 24 , 44 , 45 , 46 ]. We believe that the reason for this lies in the great sensitivity of semiconducting nanonets to their environment, which makes electrical properties unstable and weakly reproducible at first sight.…”