Fabrication of High-Resolution Nuclear Detectors Using 4H-SiC n-type Epitaxial Layers

摘要

High resolution Schottky barrier detectors for alpha particles have been fabricated on 20 μm n-type 4H-SiC epitaxial layers. Schottky barrier contact structure was accomplished by deposition of 10 nm nickel on the Si face of the epilayers. The detectors were characterized for structural, electrical, and spectroscopic properties. Scanning electron microscopy and Nomarski optical microscopy revealed a micropipe density lower than 1 cm~(-2). The current-voltage (I-V) characteristics of the device exhibited very low leakage current of the order of 6.5 pA at an operating bias of 90 V. C-V measurements revealed a typical effective doping concentrations of 2.4 × 10~(14) cm~(-3) in these epilayers. The detectors were evaluated for alpha particles detection using a ~(241)Am source. An energy resolution of ～0.98% for 5.48 MeV alpha particles was observed. The separate contribution of charge carrier drift and diffusion to the total charge collection efficiency has been calculated in these detectors following a drift-diffusion model. Detailed electronic noise analysis in terms of equivalent noise charge (ENC) was carried out to study the effect of various noise components that contribute to the total electronic noise in the detection system. Effect of shaping time, presence of source and bias on the ENC has been studied in details.