Bias-controlled spectral response in GaN/AlN single-nanowire ultraviolet photodetectors

TL;DR

This study demonstrates bias-controlled spectral response in GaN/AlN nanowire UV photodetectors, enabling selective carrier collection and enhanced UV detection through heterostructure design and bias application.

Contribution

It introduces a novel bias-dependent spectral response mechanism in GaN/AlN nanowire photodetectors, combining experimental, microscopic, and simulation analyses.

Findings

Bias polarity controls carrier collection from superlattice or base.

Enhanced UV response in specific spectral windows under different biases.

Correlation of photocurrent with structural and strain analysis.

Abstract

We present a study of GaN single-nanowire ultraviolet photodetectors with an embedded GaN/AlN superlattice. The heterostructure dimensions and doping profile were designed in such a way that the application of positive or negative bias leads to an enhancement of the collection of photogenerated carriers from the GaN/AlN superlattice or from the GaN base, respectively, as confirmed by electron beam-induced current measurements. The devices display enhanced response in the ultraviolet A ($\approx$ 330-360 nm) / B ($\approx$ 280-330 nm) spectral windows under positive/negative bias. The result is explained by correlation of the photocurrent measurements with scanning transmission electron microscopy observations of the same single nanowire, and semi-classical simulations of the strain and band structure in one and three dimensions.