Speaker
Frank Ruddy
(Ruddy Consulting)
Description
Silicon Carbide (SiC) semiconductor radiation detectors offer many advantages for measurement applications in high-temperature and high-radiation environments. In addition to possessing many of the advantages of conventional Si radiation detectors, the relatively wide band gap for SiC (3.27 eV at 300 °C for 4H-SiC) leads to detector leakage currents that are more than three orders of magnitude lower than Si at room temperature, and the leakage currents remain low at elevated temperatures allowing the detectors to operate reliably at temperatures up to 700 ºC and higher. Furthermore, SiC detectors have been shown to perform well after exposure to very high gamma-ray, charged-particle and neutron cumulative doses.
Although SiC radiation detectors were first demonstrated more than 65 years ago in 1959, the availability of suitable SiC materials hindered further development until the mid 1990’s, when high-quality SiC substrates and epitaxial layers were developed enabling a resurgence of SiC detector technology. The first SiC radiation detectors based on 4H-SiC vapor-phase epitaxy, were developed in 1995, and since then SiC detectors have been demonstrated for alpha and other charged particles, gamma rays, X-rays, beta particles and thermal and fast neutrons. SiC detector technology has emerged as a major field of research in many laboratories in many countries worldwide.
Although SiC materials technology has advanced rapidly and significantly, many limitations remain for continued development of SiC radiation detectors. A fundamental limitation of detectors produced using epitaxial layers grown on crystal substrates is the presence of defects in the epitaxial material. Although many types of defects can inhibit detector performance, the most important are point defects, which cause charge trapping. The thickness and quality of the epitaxial layer present further limitations. Although epitaxial detectors from 50 to 250 µm thick are routinely available for alpha and charged-particle detection, much higher thicknesses are required for X-ray and fast-neutron detection. These higher-thickness layers must also be achieved with low dopant concentrations (preferably 1012 Nitrogen atoms cm-3 or less) to enable full depletion at modest applied voltages. For alpha-particle and X-ray detectors, very thin Schottky or p+ contacts are required (50 Å or less), because the contact is the entrance window for the detector.
The present paper will review the history and progress of SiC detector development, discuss materials and device fabrication limitations as they effect ongoing development, and summarize the prospects and directions for future SiC detector applications.
Primary author
Frank Ruddy
(Ruddy Consulting)
