Fabrication of freestanding GaN nanobelts with enhanced ultraviolet photoresponse performance

Abstract

High-quality single component freestanding p-type and n-type GaN nanobelts were prepared by an electrochemical (EC) lift-off technique and subsequently transferred onto SiO2/Si substrates for the fabrication of high-performance ultraviolet photodetectors (UV PDs). The fabricated p-type nitrogen-polar (N-polar) GaN nanobelt UV PDs exhibited high photoresponsivity (7416.7 A/W) with a high photocurrent of 311 μA and the n-type devices presented high detectivity (1.44 × 1014 Jones) with a low dark current of 0.351 nA. Under dark condition, the thermionic field emission (TFE) and thermionic emission (TE) were found to be responsible for the current transport mechanisms of the p-type and n-type GaN nanobelt UV PDs, respectively. In addition, the enhancement of photoresponse performances in the N-polar GaN nanobelt PDs is not only attributed to their large surface-to-volume ratio but also to the strong built-in electric field. This work suggests that the rational combination of N-polar and surface effects of the freestanding GaN nanobelts is a viable approach to achieving high-performance GaN-based optoelectronic devices.