Radiation Response of Negative Gate Biased SiC MOSFETs

Abstract

Silicon carbide (SiC) metal-oxide-semiconductor field effect transistors (MOSFETs) are expected as power electronic devices for high radiative conditions, including nuclear plants and space. Radiation response of commercial-grade prototype SiC MOSFETs with applying the gate bias is of interest, in terms of installation of the device in robots or sensors working under such radioactive circumstances. Due to gamma-rays irradiation, the threshold voltages (Vth) of samples with un- and negative-biased up to −4.5 V slightly shift toward the negative voltage side. In contrast, the positive bias of 2.25 V shifts Vth more negatively. Positive charge densities trapped in the gate oxide of un- and positive-biased samples increased with increasing dose. However, no significant increase was observed for negative-biased samples of −2.25 and −4.5 V. We calculated characteristic parameters for the accumulation of holes in the gate oxide, σpJp which is defined as the product of current density due to holes generated by irradiation and capture cross section for a hole in a trap, and it is lower for these negative biased samples compared with the unbiased case. Application of appropriate negative gate biases to SiC MOSFETs during irradiation suppresses accumulation of positive charges in the gate oxide and negative shift of Vth, due to irradiation.

Impact of low-dose radiation on nitrided lateral 4H-SiC MOSFETs and the related mechanisms

“…[25,26] We attribute the large fluctuation of V th at low-dose irradiation (< 100 krad) to the intense competitive relationship between radiation-induced oxide trapped charges and radiationinduced interface traps, and the corresponding trapping mechanism will be discussed in Subsection 3.4. To our knowledge, little work has observed positive V th shifts of SiC MOSFETs after irradiation; we think it is probably because the previous works mainly focus on the radiation effect under a relatively high γ-ray radiation dose (typically > 300 krad) [9,19] due to the strong radiation tolerance of SiC. Additionally, it is worth mentioning that we have tested other devices (fabricated with the same structure and processing method) under similar irradiation conditions.…”

“…Additionally, previous works mainly focused on the radiation effect under a relatively high radiation dose (typically > 300 krad). [9,18,19] However, according to biastemperature instability research, interface traps tend to have a significant impact on the electrical characteristics of the 4H-SiC MOSFETs, especially in the early stage of operation. [20] Thus, the effect of charge trapping at low doses may be nonnegligible, which also needs to be intensively investigated.…”

Influence of Different Device Structures on the Degradation for Trench-Gate SiC MOSFETs: Taking Avalanche Stress as an Example

“…With etching, oxidation, and other critical processing technologies becoming more and more mature, SiC metal-oxide-semiconductor field effect transistors (MOSFETs) are gradually applied to power electronic fields to replace traditional silicon power devices [1][2][3][4]. Numerous SiC MOSFET products have been pushed into the market [5][6][7].…”

Impact of switching frequencies on the TID response of SiC power MOSFETs

“…In the space radiation environment, the total ionizing dose (TID) induced by gamma rays is one of the most important factors that cause the failure of electronic devices. Recently, the radiation response of SiC power MOSFETs to gamma ray irradiation has been studied by several authors [4][5][6][7][8] since SiC high-voltage power MOSFETs have become commercially available. Thus far, the radiation response has been studied in terms of irradiation conditions, such as the temperature [4][5][6] and application of gate bias [7][8][9] .…”