Radiation Defects and Carrier Lifetime in 4H-SiC Bipolar Devices

Abstract

The effect of radiation damage on the minority carrier lifetime in the 4 H-SiC epilayers forming the n-base of the power p-i-n diodes is presented. Irradiation with fast neutrons and MeV protons is used for uniform and local lifetime reduction. Deep-level transient spectroscopy in combination with open-circuit voltage decay measurement shows that the carrier lifetime is reduced by increased carrier recombination on Z(1)/Z(2), EH3, and possibly RD4 levels. The lifetime degrades swiftly and the ON-state carrier modulation capability of high-voltage devices can be easily lost already at very low fluences. The results further show that the proton irradiation provides an excellent tool for local lifetime tailoring. The carrier lifetime can be easily set by proton fluence and localized by proton energy. The proper local lifetime reduction speeds up diode recovery without an undesirable increase in the forward voltage drop. However, attention must be taken to properly locate the damage maximum so as not to increase device leakage.