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

This letter reports the first characterization of InAlN/GaN-on-Si solid-state detectors under ultra-high dose-per-pulse (UH-DPP) electron irradiation for FLASH radiotherapy applications. Unpassivated Ni/Au metal-semiconductor-metal (MSM) and two-dimensional electron gas (2DEG) interdigital 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 (SNR) exceeding 220 under 2 Gy pulses. Across a dose-per-pulse (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 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.