The Impact of Non-Ideal Ohmic Contacts on the Performance of High-Voltage SiC MPS Diodes

Abstract

The wide band gap of SiC semiconductor devices constitutes a serious challenge to build good Ohmic contacts on the surface of the p-type material. This is reflected in the numerical analysis of ”realistic” devices, where we have to cope with serious problems, such as a shifting threshold voltage, reduced forward conductivity, and no noticeable conductivity modulation by minority carrier injection from p+-emitters, in matching measured data with simulation results, as a consequence of the significant impact of non-ideal poor Ohmic contacts. In this work, we used a Schottky contact model together with a barrier tunneling model, instead of common ideal Ohmic contact model, to simulate the non-ideal Ohmic contact on SiC MPS diodes. Based on this approach, the I-V characteristics of real Ohmic contacts can be reproduced in high-fidelity simulations, providing us physical insight of the observed operational behavior.

Temperature Dependence of the Bipolar Activation and the Leakage Currents of 10 kV 4H-SiC JBS-Diodes

“…We found that the Schottky barrier of JBS-diode II is almost 1 eV higher than that of JBSdiode I. The increase of this potential barrier with decreasing ratio Ws/WPin can be attributed to the depletion layers along the p + n --junctions, which have to recede before electrons can flow from the Schottky contact to the drift zone [4]. Fig.…”

International Journal of Electronics and Telecommunications

“…Exploiting the potential of silicon carbide electrophysical parameters requires from ohmic contacts to SiC-based devices demonstration of low resistivity, stable electrical conductivity, high oxidation resistance and reliability, especially when operating at elevated temperatures. Insufficient electrical conductivity of ohmic contacts due to degradation of metal/SiC interface or relatively high specific contact resistance ρc (>10 -3 Ωcm 2 ) may result in an unacceptably high voltage drop at the contact, and thereby deterioration or even making impossible operation of silicon carbide devices [3,4].…”