Time Resolution of a Novel Ultra-fast Graphene-Optimized 4H-SiC PIN

Abstract: Silicon carbide detectors exhibit good detection performance such as fast time resolution, high radiation tolerances, high breakdown voltage and low temperature sensitivity and have been studied for detection applications. Meanwhile, transient current technique (TCT) is a direct and effective method to evaluate the time resolution of semiconductor detectors. Conventional metal electrodes for TCT testing employ window structures, which lead to non-uniform electric field distribution and deteriorated time resolution. Graphene features high optical transmittance, ultrahigh carrier mobility, and excellent radiation resistance, making it an ideal transparent electrode material for semiconductor detectors. In this work, a graphene-optimized ring electrode (G/RE) 4H-SiC PIN detector and a reference ring electrode (RE) 4H-SiC PIN detector are fabricated. TCT measurements demonstrate that graphene integration improves the time resolution consistency, reducing the time resolution from 38 ps (reference RE detector) to 21 ps (G/RE detector) at the maximum scanning distance, while also achieving effective noise suppression. The graphene integration improves the stability of time resolution by 87% compared to the reference detector. Notably, the achieved time resolution of 21 ps is comparable to that of state-of-the-art 4H-SiC low-gain avalanche detectors (LGADs), which typically exhibit time resolutions better than 35 ps under single minimum ionizing particle (MIP) equivalent injection conditions, further validating the effectiveness of graphene-based electrode design.