Design, Fabrication, Characterization, and Evaluation of X-ray Detectors Based on n-type 4H-SiC Epitaxial Layer

Progress of high resolution radiation detectors requires the fabrication of radiation detectors that are capable of reliable, long term non-degrading operation at elevated temperatures under high doses of ionizing radiation. One of the semiconductor materials upon which such detectors can be based on is silicon carbide (SiC). The substantial advances in the development of SiC technology over the last 25 years have made it possible to develop almost all the basic types of semiconductor devices including radiation detectors based on SiC. Diode-type detectors fabricated using SiC epitaxial layers perform well in high-resolution detection of low penetration depth radiation (i.e. alpha, beta, soft x-rays). Available SiC epilayers have a maximum thickness in the order of 100 μm with a residual n-type doping ~ 10 cm that limits the depth of the depletion layer (detector’s active region) to less than 100 μm at reasonable bias voltages. This poses a limitation in the detection of high energy x-rays and γ-rays by this type of detectors. An alternative type of SiC detectors utilizes bulk semi-insulating SiC crystals. These crystals can be grown by physical vapor transport (PVT) or high temperature chemical vapor deposition (HTCVD) methods. At present the resolution of the detectors based on PVT-grown SI SiC is not adequate presumably due to high density of defects and deep level centers, implying that further quality improvement of PVT-grown SiC crystals is necessary. Past studies of