Lifetime of holes determination in 4H-SiC using two-photon optical beam induced current method

Abstract

Wide bandgap semiconductors such as silicon carbide, gallium nitride and diamond have been recently investigated in order to replace silicon in the power electronic domain. In this paper, silicon carbide devices are studied using an optical method. It consists on illuminating a reverse biased junction with a laser beam with an appropriate wavelength, and then measuring the induced current due to the photon absorption. According to the wavelength, one- or two-photon absorption is triggered when photon energy is respectively higher or lower than the semiconductor bandgap. In the latter case, the probability of electron hole pair (EHP) generation is very small, which leads to use a powerful incident beam. In this paper, two-photon generation is used in order to determine the lifetime of minority charge carriers in N doped 4H-SiC. The incident beam is a pulsed green source with a wavelength of 532 nm and a high power density that can reach up to 6 GW.cm-2. Test devices are PN diodes protected by a junction termination extension (JTE). Results show a hole's lifetime of 730 ns.