【Device Papers】Bias-Dependent Transient Overshoot in α-Ga₂O₃ MSM X-Ray Detectors Interpreted through Device-Level Transport–Relaxation Competition

      Researchers from Korea Aerospace University have published a dissertation titled " Bias-Dependent Transient Overshoot in α-Ga₂O₃ MSM X-Ray Detectors Interpreted through Device-Level Transport–Relaxation Competition " in Materials Chemistry and Physics.

Abstract

      The bias-dependent transient photocurrent response of symmetric Ti/Ti α-Ga₂O₃ metal–semiconductor–metal X-ray detectors is systematically investigated. At low bias, the detector exhibits a pronounced initial current overshoot followed by a gradual approach to the steady-state photocurrent. The overshoot amplitude decreases markedly with increasing applied voltage and becomes negligible at 15 V. In contrast, the phenomenologically fitted post-peak decay constant (τ_fit) remains within approximately 11–15 s over the 1–10 V range and does not show a corresponding decrease. The decoupled voltage dependences of the overshoot amplitude and τ_fit indicate that overshoot suppression is not accompanied by an acceleration of the measured post-peak decay.

Notably, this behavior contrasts with previously reported Ga₂O₃ X-ray detectors in which overshoot emerges or becomes more pronounced at high bias. The present α-Ga₂O₃ MSM detector instead exhibits its strongest overshoot at low bias, followed by progressive suppression as the electric field increases. This opposite bias dependence reveals that transient overshoot is not a universal high-field instability in Ga₂O₃ detectors, but is strongly influenced by the material phase, device configuration, and carrier-collection conditions. The observations are consistent with a device-level transition from transient mobile-carrier accumulation under relatively inefficient low-field collection to more effective field-driven carrier collection at higher bias. These findings identify bias-dependent overshoot as a useful probe of the interplay between carrier redistribution and collection in Ga₂O₃ X-ray detectors and provide guidance for achieving stable, overshoot-free operation.

DOI：

https://doi.org/10.1016/j.matchemphys.2026.132965