Silicon Carbide Detectors for in vivo Dosimetry

Semiconductor detectors for in vivo dosimetry have served in recent years as an important part of quality assurance for radiotherapy. Silicon carbide (SiC) can represent a better semiconductor with respect to the more popular silicon (Si) thanks to its physical characteristics such as wide bandgap, high electron saturation velocity, lower effective atomic number, and high radiation resistance to X and gamma rays. In this article we present an investigation aimed at characterizing 4H-SiC epitaxial Schottky diodes as in vivo dosimeters. The electrical characterization at room temperature showed ultra low leakage current densities as low as 0.1 pA/cm ² at 100 V bias with negligible dependence on temperature. The SiC diode was tested as radiotherapy dosimeter using 6 MV photon beams from a linear accelerator in a typical clinical setting. Collected charge as a function of exposed radiation dose were measured and compared to three standard commercially available silicon dosimeters. A sensitivity of 23 nC/Gy with linearity errors within ±0.5% and time stability of 0.6% were achieved. No negligible effects on the diode I-V characteristics after irradiation were observed.