High-resolution GaN p-i-n alpha-particle detector with thick i-GaN layer

Alpha-particle detectors face several fundamental challenges, including the difficulty in achieving thick, high-quality depletion regions essential for efficient charge collection, high leakage currents caused by material defects, and severe energy loss in conventional electrode configurations. To address these limitations, we developed a GaN p-i-n alpha-particle detector on a free-standing substrate with a 20 μm thick intrinsic layer. A grid-shaped front electrode is introduced to minimize dead-layer energy loss. The device achieves full depletion at a low bias of −40 V and maintains leakage currents below several tens of picoampere up to −100 V. Notably, it exhibits an energy resolution of 1.5% at just −10 V, as well as a charge collection efficiency of 83.6%, which increases to 98.1% at −70 V. Theoretical modeling further reveals the underlying mechanism behind the anomalous energy resolution trend. These advances are attributed to the high crystalline quality of the thick i-GaN layer and the grid-shaped electrode design, which collectively suppress dislocation-induced leakage and dead-layer effects. This work provides a practical pathway to low-voltage, high-performance GaN alpha-particle detectors.