Engineering the Schottky Interface of 3.3 kV SiC JBS Diodes Using a P2O5 Surface Passivation Treatment

Abstract

A systematic study is presented into the impact of a P2O5 surface passivation treatment, carried out prior to the deposition of a high refactory metal contact to 3.3 kV JBS diodes. Electrical results from Mo, W and Nb diodes reveal that those diodes that undergo the treatment have a major leakage current reduction, most significantly by 3.5 orders of magnitude to 1.5×10-6 A x cm-2 for treated W diodes. When applied to fully optimized 3.3 kV Mo/SiC JBS diodes, the P2O5 surface passivation treatment reduces the apparent barrier height, as well as the leakage current. SIMS analysis reveals that during the treatment, phosphorous diffuses into the top 50 nm of the SiC, achieving a peak density of 1019 cm-3, while XPS results suggest some of this diffuses into the contact metal during the contact anneal, altering the Schottky barrier height. TCAD simulations help give more insight into band diagram changes at the Schottky interface, where the partial activation of the phosphorous ions is shown to alter the Schottky barrier, promoting a thermionic field emission conduction, effectively lowering the barrier height at the interface in Mo/4H-SiC diodes.