Revisiting BPW34 photodiodes as proton dosimeters

The BPW34 photodiode, a widely available commercial off-the-shelf device, is evaluated for its potential as a proton dosimeter through an integrated approach combining electrical, optical, and defect-level analyses. Proton irradiation at 96.6 MeV produces a linear increase in dark current with fluence, consistent with the Non-Ionizing Energy Loss (NIEL) hypothesis. Forward and reverse I–V measurements indicate increased leakage current and a degradation in series resistance, while External Quantum Efficiency (EQE) and open circuit voltage decay data reveal pronounced carrier-lifetime losses from radiation-induced traps. Notably, EQE variations show a strong correspondence with displacement damage trends, suggesting that the optical response could indirectly serve as a probe for NIEL dose assessment. The study also examines the dependence of degradation on proton energy. DLTS measurements identify at least two dominant defect states: tri-vacancy clusters and oxygen-vacancy complexes bridging the link between microscopic lattice disorder and macroscopic performance loss. Complementing the experiments, a Geant4-based G4SEE simulation provides, for the first time in the context of BPW34, a detailed NIEL analysis that resolves the contribution of secondary species such as Mg, O, and Si to displacement damage.