Fundamental Mechanisms of Total-Ionizing-Dose Degradation in Waveguide-Coupled Germanium-on-Silicon p-i-n Photodiodes

Musibau, SolomonSolomonMusibauArnold, Kellen P.Kellen P.ArnoldVeluri, Anurag R.Anurag R.VeluriTsiara, ArtemisiaArtemisiaTsiaraFranco, JacopoJacopoFrancoCroes, KristofKristofCroesLinten, DimitriDimitriLintenVan Campenhout, JorisJorisVan CampenhoutWeiss, Sharon M.Sharon M.WeissSchrimpf, Ronald D.Ronald D.SchrimpfFleetwood, Daniel M.Daniel M.FleetwoodKosier, Steven L.Steven L.KosierDe Wolf, IngridIngridDe WolfReed, Robert A.Robert A.Reed2026-07-272026-07-2720260018-94991558-1578https://imec-publications.be/handle/20.500.12860/60008In this work, we investigate 10-keV X-ray-induced total ionizing dose (TID) effects in vertical p-in (VPIN) photodiodes (PDs) using calibrated TCAD simulations. We demonstrate that positive trapped charges near the space-charge region locally increase the electric field magnitude, enhancing Shockley–Read–Hall (SRH) generation–recombination and trap-assisted tunneling (TAT) rates, thereby impacting dark current, forward current, and the ideality factor. Simulations indicate that charge trapping at the top-corner Ge/SiO2 interfaces accurately reproduces experimental trends. In contrast, photocurrent and junction capacitance remain largely unaffected, attributed to the large area-to-perimeter ratio of the device, which reduces the influence of localized interface degradation.engFundamental Mechanisms of Total-Ionizing-Dose Degradation in Waveguide-Coupled Germanium-on-Silicon p-i-n PhotodiodesJournal article10.1109/tns.2025.3628718WOS:001756824900001RADIATIONDEFECTSDAMAGE1558-1578