Defect Electronics in SiC and Fabrication of Ultrahigh-Voltage Bipolar Devices

Abstract

Fast epitaxial growth, defect reduction, device designing, and process development in SiC toward ultrahigh-voltage (> 10 kV) bipolar devices are investigated. 100~200 um-thick 4H-SiC epilayers with a low background doping concentration in the low 10^{13} cm^{-3} can be grown at a growth rate greater than 50 um/h. Impacts of extended defects on carrier recombination are clarified in photoluminescence mapping measurements. Generation and reduction of Z_{1/2} center, the dominant lifetime killer, are summarized. After Z_{1/2} elimination by thermal oxidation at 1400^{o}C, the carrier lifetime can be enhanced to 25 us or even longer. By utilizing space-modulated junction termination extension, a 21.7 kV PiN diode is demonstrated. Through unique process development, the current gain in bipolar junction transistors is increased to 250~330.