Field-Effect Transistors Based on Silicon Nanowire Arrays: Effect of the Good and the Bad Silicon Nanowires

Aligned arrays of silicon nanowires (aa-Si NWs) allow the exploitation of Si NWs in a scalable way. Previous studies explored the influence of the Si NWs' number, doping density, and diameter on the related electrical performance. Nevertheless, the origin of the observed effects still not fully understood. Here, we aim to provide an understanding on the effect of channel number on the fundamental parameters of aa-Si NW field effect transistors (FETs). Toward this end, we have fabricated and characterized 87 FET devices with varied number of Si NWs, which were grown by chemical vapor deposition with gold catalyst. The results show that FETs with Si NWs above a threshold number (n > 80) exhibit better device uniformity, but generally lower device performance, than FETs with lower number of Si NWs (3 <= n < 80). Complementary analysis indicates that the obtained discrepancies could be explained by a weighted contribution of two main groups of Si NWs: (i) a group of gold free Si NWs that exhibit high and uniform electrical characteristics; and (ii) a group of gold doped Si NWs that exhibit inferior electrical characteristics. These findings are validated by a binomial model that consider the aa-Si NW FETs via a weighted combination of FETs of individual Si NWs. Overall, the obtained results suggest that the criterions used currently for evaluating the device performance (e.g., uniform diameter, length, and shape of Si NWs) do not necessarily guarantee uniform or satisfying electrical characteristics, raising the need for new growth processes and/or advanced sorting techniques of electrically homogeneous Si NWs.