Influence of intrinsic defects on 4H-SiC device performances

Abstract

4H-SiC, a wide bandgap semiconductor, exhibits numerous excellent properties that make it widely used in the electronics industry. However, intrinsic defects within the semiconductor can negatively impact its electrical performance. Carbon vacancies, a type of intrinsic defect in 4H-SiC, are known for their adverse effects on minority carrier lifetime, breakdown electric field, and leakage current. Since its influence on the electrical performance, suppressing the formation of carbon vacancy is essential in the fabrication of 4H-SiC device. The Junction Barrier Schottky (JBS) diode, an optimized version of the Schottky barrier diode, is a significant application of 4H-SiC. Aiming at improving the electrical performance of JBS diode, this study optimized its fabrication process by employing a lower annealing temperature and depositing a sacrificial oxide layer after annealing, significantly reducing the device's concentration of carbon vacancy and leakage current.

Deep level transient spectroscopy (DLTS) and cathodoluminescence (CL) measurements were used to characterize defects in the samples. The DLTS results showed a significant reduction in the concentration of defects with an activation energy of 0.68 eV, associated with carbon vacancies, in the JBS diode prepared using the improved method. Additionally, CL measurement results indicated that the CL spectra of samples prepared by the new method lacked the emission peak with a photon energy of 2.62 eV, which is also related to carbon vacancies.

Moreover, fitting the IV data with Poole-Frenkel (PF) emission revealed that the leakage current in the JBS diode is associated with carbon vacancies. By correlating the CL spectra with leakage current, a connection among carbon vacancy, CL signal and leakage current was established. This provides new insights into detecting leakage current during the fabrication process of 4H-SiC devices.