An SiC/GaN detector/front-end detection system for high-resolution alpha-particle spectroscopy

An alpha-particle spectrometer has been assembled, consisting of an epitaxial 50 mu m thick 4H silicon carbide (SiC) detector connected to a gallium-nitride (GaN) high-electron mobility transistor (HEMT) used as input transistor of the front-end electronics. The depleted layer of the SiC diode detector was sufficient to stop all alpha particles in the 4.8-MeV to 5.8-MeV energy range. An excellent energy resolution of similar to 0.9% has been obtained in this energy range at a temperature of 55 degrees C. The energy-resolution limiting factor is found to be the dispersion of the energy loss in the gold Schottky contact, which acts as entrance window to the detector. We used a GaN front-end transistor because this material offers two important advantages over silicon: 1) it is a wide bandgap semiconductor and therefore is intrinsically more desirable for room and above-room temperature operation and 2) it can be grown on SiC substrates so as to realize SiC/GaN integrated systems. SiG-detector spectrometers are interesting in many nuclear applications where the operation environment is hostile, both in terms of ionising radiations and of high temperatures. Such applications include monitoring of ionising radiations in nuclear power plants and beam diagnostic in fundamental nuclear physics experiments.