Effect of Z1/2, EH5, and Ci1 deep defects on the performance of n-type 4H-SiC epitaxial layers Schottky detectors: Alpha spectroscopy and deep level transient spectroscopy studies

Abstract

Spectroscopic performance of Schottky barrier alpha particle detectors fabricated on 50 μm thick n-type 4H-SiC epitaxial layers containing Z1/2, EH5, and Ci1 deep levels were investigated. The device performance was evaluated on the basis of junction current/capacitance characterization and alpha pulse-height spectroscopy. Capacitance mode deep level transient spectroscopy revealed the presence of the above-mentioned deep levels along with two shallow level defects related to titanium impurities (Ti(h) and Ti(c)) and an unidentified deep electron trap located at 2.4 eV below the conduction band minimum, which is being reported for the first time. The concentration of the lifetime killer Z1/2 defects was found to be 1.7 × 1013 cm−3. The charge transport and collection efficiency results obtained from the alpha particle pulse-height spectroscopy were interpreted using a drift-diffusion charge transport model. Based on these investigations, the physics behind the correlation of the detector properties viz., energy resolution and charge collection efficiency, the junction properties like uniformity in barrier-height, leakage current, and effective doping concentration, and the presence of defects has been discussed in details. The studies also revealed that the dominating contribution to the charge collection efficiency was due to the diffusion of charge carriers generated in the neutral region of the detector. The 10 mm2 large area detectors demonstrated an impressive energy resolution of 1.8% for 5486 keV alpha particles at an optimized operating reverse bias of 130 V.