Development and Performance Study of Vertical GaN $\alpha$-Particle Detector with High Energy Resolution

TL;DR

This paper reports on a vertical GaN alpha-particle detector with ultralow leakage current and high energy resolution, highlighting the role of depletion-width nonuniformity in spectral tailing and offering design insights.

Contribution

It introduces a GaN detector with ultrathin dead layer and guard-ring, and demonstrates for the first time that depletion-width nonuniformity causes low-energy tailing.

Findings

Detector achieves 2.69% energy resolution at -260 V.

Depletion-width nonuniformity identified as main cause of low-energy tail.

Good agreement between Geant4 simulations and experimental results.

Abstract

High-energy-resolution GaN $\alpha$-particle detectors have significant potential for space radiation, nuclear instrumentation, and harsh-environment applications. However, existing GaN $\alpha$-particle detectors still face several key challenges, including reducing the dead-layer thickness, suppressing leakage current under high reverse bias, improving energy resolution, and clarifying the physical mechanism underlying the low-energy tail phenomenon. This study presents a vertical homoepitaxial GaN $\alpha$-particle detector integrating a 20-nm ultrathin dead layer and a guard-ring structure. The detector exhibits an ultralow leakage current of 2.195 nA at -200 V and an intrinsic energy resolution of 2.69% with a charge collection efficiency (CCE) of 95.9% at -260 V. More importantly, this work demonstrates for the first time through Geant4 simulations that depletion-width nonuniformity is the dominant source of partial energy leakage, leading to an extended low-energy tail in the energy spectrum. We establish a depletion-width nonuniformity model and observe good agreement between simulation and experiment. This finding provides practical guidance for the design and optimization of high-performance GaN-based radiation detectors.