Anomalous Decrease of Field-Emission Tunneling Current for Poly-Si/4H-SiC Power Heterojunction Under Reverse Bias Stress

Abstract

The reliability of the low-barrier Poly-Si/4H-SiC heterojunction is experimentally demonstrated for the first time, with a superior long-term forward conduction and reverse blocking reliability under the 500-A/cm2 forward current density and the 1-MV/cm reverse electric field, respectively, which is critical for power applications. The pure power heterojunction is fabricated on a 1.2 kV-class 4H-SiC epilayer, featuring a barrier height of 0.804 eV and a great ideality factor of 1.026. It is innovatively discovered that the heterojunction reverse current ( ${I}_{\text {R}}\text {)}$ anomalously decreases with the reverse bias stress time without any forward electrical parameter degradation. By modelling the heterojunction field-emission (FE) tunneling and extracting the defect density, it is demonstrated that the deep-level acceptor-type interface defects are activated by the reverse electric field, which will capture electrons and impede the reverse FE tunneling current. The research results can promote the power applications of the Poly-Si/4H-SiC heterojunction and provide guidelines for all heterojunction devices in the burn-in process and the reliability evaluation.