InAlN/GaN Detectors for Real-Time Dosimetry in Ultra-High Dose Rate FLASH Radiotherapy

This letter reports the first characterization of InAlN/gallium nitride (GaN)-on-Si solid-state detectors under ultra-high dose-per-pulse (DPP) electron irradiation for FLASH radiotherapy applications. Unpassivated Ni/Au metal-semiconductor-metal and 2-D electron gas (2DEG) interdigitated transducer (IDT) detectors exhibited the best transient performance, with the 2DEG IDT resolving individual pulses as short as 3 μs rise and 325 μs fall times and achieving a signal-to-noise ratio exceeding 220 under 2 Gy pulses. Across a DPP range of 0.05-0.5 Gy, the 2DEG IDT detector demonstrated consistent, dose-dependent voltage responses with sensitivities of 0.5-0.9 V/Gy and a normalized sensitivity of 48.75 nC/Gy/mm2, one to two orders of magnitude higher than reported silicon carbide (SiC) and diamond detectors. These results establish InAlN/GaN detectors as promising candidates for compact, high-speed, and radiation-tolerant dosimetry systems capable of real-time single-pulse monitoring in clinical FLASH radiotherapy.