Negative Capacitance Phenomenon in GaAs-Based MIS Devices Under Ionizing Radiation

Abstract

This study focuses on the abnormal peaks observed in voltage-dependent capacitance graphs and negative capacitance behaviors of the GaAs-based MOS devices for the unirradiated sample and after exposing the device to 5 and 10 kGy ionizing (gamma) radiation doses. Experimental results showed that the amplitude of the abnormal peaks, observed at about 1.75 V, increases with the irradiation dose. The peak point was also shifted toward the positive biases after irradiation. Furthermore, the conductance values increased rapidly and reached their maximum level, while the capacitance values reached their minimum level in the high voltage biases. This situation is directly related to the inductive behavior of the MOS devices. However, it has been determined that the MOS device's inductive behavior is more effective after irradiation. These behaviors can be observed because of the ionization process, the MOS device's series resistance, surface states, and due to some displacement damages caused by ionizing radiation. Therefore, the series resistance and the radiation-induced surface states were obtained to clarify the impact of radiation on the device. It was seen that the radiation-induced surface states changed around 3x1012 for the maximum cumulative dose (10 kGy), and the series resistance values changed less than 2 Ω (it was obtained 8.74 Ω for 0 kGy and 6.82 Ω for 10 kGy). As a result, the degradation in the GaAs-based MOS device was determined to be insignificant for 10 kGy doses. Therefore, this MOS device can be safely used as an electronic component in radiation environments such as nuclear plants and satellite systems.