Environmental sensitivity of n-i-n and undoped single GaN nanowire photodetectors

TL;DR

This study compares the environmental sensitivity of undoped and n-i-n GaN nanowire photodetectors, revealing how surface states and Fermi level pinning influence their performance and stability under different conditions.

Contribution

It provides a comparative analysis of undoped and n-i-n GaN nanowire photodetectors, highlighting the effects of surface states and Fermi level pinning on their environmental response.

Findings

Undoped NWs show increased responsivity and persistent photoconductivity in vacuum.

Air adsorbed oxygen affects carrier dynamics and reduces photoresponse.

Fermi level pinning in n-i-n NWs limits environmental sensitivity and persistent effects.

Abstract

In this work, we compare the photodetector performance of single defect-free undoped and n-in GaN nanowires (NWs). In vacuum, undoped NWs present a responsivity increment, nonlinearities and persistent photoconductivity effects (~ 100 s). Their unpinned Fermi level at the m-plane NW sidewalls enhances the surface states role in the photodetection dynamics. Air adsorbed oxygen accelerates the carrier dynamics at the price of reducing the photoresponse. In contrast, in n-i-n NWs, the Fermi level pinning at the contact regions limits the photoinduced sweep of the surface band bending, and hence reduces the environment sensitivity and prevents persistent effects even in vacuum.