Nonpolar p-GaN/n-Si heterojunction diode characteristics: A comparison between ensemble and single nanowire devices

TL;DR

This study compares the electrical and photodiode performance of ensemble versus single p-GaN nanowire/n-Si heterojunction devices, revealing significant differences in ideality factors, fill-factors, and photoresponse due to defect states and inhomogeneity.

Contribution

It provides a detailed comparison highlighting the impact of nanowire ensemble inhomogeneity and defect states on device performance, which is novel.

Findings

Single nanowire devices have lower ideality factors than ensemble devices.

Ensemble nanowire devices show higher fill-factors in photovoltaic mode.

Single nanowire devices exhibit a five-order increase in responsivity at 470 nm.

Abstract

The electrical and photodiode characteristics of ensemble and single p-GaN nanowire and n-Si heterojunction devices were studied. Ideality factor of the single nanowire p-GaN/n-Si device was found to be about three times lower compared to that of the ensemble nanowire device. Apart from the deep-level traps in p-GaN nanowires, defect states due to inhomogeneity in Mg dopants in the ensemble nanowire device are attributed to the origin of high ideality factor. Photovoltaic mode of ensemble nanowire device showed an improvement in the fill-factors up to 60 percent over the single nanowire device with fill-factors up to 30 percent. Reponsivity of the single nanowire device in photoconducting mode was found to be enhanced by five orders, at 470 nm. The enhanced photoresponse of the single nanowire device also confirms the photoconduction due to defect states in p-GaN nanowires.