Evaluation of surface recombination of SiC for development of bipolar devices

Abstract

Ultra-high voltage power devices are employed for management of power networks. Si-based semiconductor devices have been developed for such the power devices. Maximum breakdown voltages of Si devices are of the order of kV. When the voltage in the power network was higher than the breakdown voltage of the devices, the devices were connected in series. The series connection introduces high resistance and power loss. To overcome this series resistance problem, it has been suggested that utilization of silicon carbide (SiC) devices. SiC has much higher breakdown electric field than Si, and thus high voltage in the power networks can be managed by SiC device without the series connection. Therefore, development of ultra-high voltage SiC device will decrease resistance and power loss in the power networks. However, there are several difficulties to develop ultra-high voltage SiC devices. One of the difficulties is control of the carrier lifetime. In fact, ultra-high voltage devices are fabricated with bipolar structure, and, in the bipolar devices, the carrier lifetime is highly influential on resistance and power loss. The carrier lifetime is limited by several factors, and one of the most important factors is the surface recombination. Therefore, evaluation and control of the surface recombination is essential to develop ultra-high voltage SiC devices. In this paper, we will report evaluation techniques for the surface recombination of SiC. In addition, dependence of the surface recombination on surface treatments, crystal faces and temperature are shown. The evaluated surface recombination velocities will support development of ultra-high voltage SiC devices.