Space-charge-limited effect on the temperature-dependent performance of Fe-doped <i>β</i> -Ga2O3 x-ray detector

Abstract

In this paper, a vertical x-ray detector was fabricated using high-resistivity Fe-doped beta-gallium oxide (β-Ga2O3) material, and the x-ray response current–voltage characteristics were measured over a temperature range from 300 to 450 K. The dark current of the detector exhibited different slopes with bias voltage on a double-logarithmic scale, consistent with the space-charge-limited current (SCLC) mechanism at 300 K. This phenomenon resulted from the accumulation of space charge, arising from the capture and regulation of injected carriers. Under x-ray illumination, the nonequilibrium carriers generated by the x-ray were captured and trapped, thereby generating space charge and leading to space-charge-limited photocurrent (SCLP) during the x-ray response process. In this case, the output net current of the Fe-doped β-Ga2O3 x-ray detector showed non-monotonic temperature dependence. Initially, as the temperature increased, the net output current decreased, likely due to increased carrier thermal generation and the influence of traps within the material. Notably, the output net current began to rise above a threshold temperature, indicating enhanced performance at higher temperatures. This enhancement was caused by the release of trapped carriers, which enabled more free carriers to participate in SCLP transport, leading to a stronger response. However, at 450 K, the dark current increased rapidly, and thermally activated carriers dominated, rendering the SCLC mechanism ineffective. This phenomenon highlights the complex interplay between the thermal activation of carriers and the space-charge-limited mechanism in the high-resistivity, compensated monocrystal β-Ga2O3-based x-ray detector under x-ray illumination at elevated temperatures.