Off-State Negative Differential Capacitance AlGaN/GaN Heterostructures in cryogenic temperature

There are few reports on the degradation phenomenon and mechanism of AlGaN/GaN heterojunction field-effect transistors (HFETs) operating at cryogenic temperature. In this paper, the off-state capacitance of AlGaN / GaN HFETs at cryogenic temperature and the room temperature was investigated. The negative differential capacitance at 77 Κ and 300 Κ is 11.26 F and 0.69 F, respectively. The capacitance was tested at different temperatures, which showed that the negative differential capacitance came from low-temperature conditions. At room temperature, the resistance was increased sharply under the gate of the device off-state. At this time, the current leakage channel was turned on, the phenomenon of negative differential capacitance was caused by an accumulation of electrons. Through the C-V test at different frequencies at 77 K, it reflects the relationship between the trap level, the off-state leakage current, and the negative differential capacitance. This article provides suggestions for the application of GaN-based radio frequency devices in cryogenic temperature environments.

I. Introduction

GaN-based heterostructure field-effect transistors (HFETs) have the advantages of high-power density, high efficiency, and compact size, and are therefore candidates for high-speed electronic power devices.[l–3] The reliability of device is critical to commercialization. Therefore, the temperature-dependent study is an essential part of the comprehensive characterization of the AlGaN/GaN HFETs. With the continuous deepening of research, AlGaN/GaN HFETs devices are gradually moving from the laboratory to practical applications, especially in the fields of national defense construction, aviation, aerospace, and space exploration. However, due to the wide range of temperature changes in the space environment, and the large range of changes, when the spacecraft flies in space, it will be in a constant alternation of extremely low temperature and extremely high temperature. For example, in the absence of light, the temperature of outer space will be lower than minus 200°C, and in the case of light, the temperature of the outer space environment will be higher than 100°C For the spacecraft to maintain long-term stable operation, the devices used need to have very high-temperature reliability[4, 5]. Not only can they meet the working requirements under high-temperature conditions, but the device performance should also maintain a high degree of consistency under low and extremely low-temperature conditions. Therefore, the research on the temperature reliability of GaN HFETs devices, in addition to the current mature high-temperature field, also needs to pay great attention to the changes in device performance at low or even extremely low temperatures[6– 8].