Cross‐Sectional Carrier Lifetime Profiling and Deep Level Monitoring in Silicon Carbide Films Exhibiting Variable Carbon Vacancy Concentrations

Abstract

Silicon carbide (SiC) is a wide bandgap semiconductor with material properties allowing for electronic applications operating under harsh conditions, such as high temperature and radiation.Among the key challenges yet to be resolved is mastering and control of the electrically active point defects, particularly in the technologically most relevant 4H-SiC polytype. The point defects spontaneously generated in a radiation-hard environment usually shorten the carrier lifetime degrading the performance of power electronics and radiation sensors. In contrast, the irradiation by swift ions, e.g., by MeV protons, can be used as a tool for the controlled introduction of radiation-defect-related recombination centers for optimizing lifetime and dynamic characteristics. [1] Still, the longest possible minority carrier lifetime in 4H-SiC epitaxial layers is the key prerequisite for the realization of high-voltage bipolar power devices; e.g., to modulate carrier conductivity in the voltage-blocking layer of a 10 kV class device comprised of 100 μm thick epilayer with doping concentration %10 15 cm À3 , the required carrier lifetime is in the range of 10 μs. In recent years, carrier lifetimes in excess of several microseconds are being demonstrated after the origin of inherently short (sub-microsecond) lifetimes has been associated with intrinsic point defect, carbon vacancy (V C ), acting as a lifetime killer. [2] In response, several remedies to diminish such defects have been developed, such as carbon implantation, high-temperature oxidation, and thermal equilibration in carbon-rich conditions. [3][4][5][6] In 4H-SiC, V C exhibits electrical