A comprehensive study on usage of Gd2O3 dielectric in MOS based radiation sensors considering frequency dependent radiation response

Abstract

The purpose of this study is to investigate the Gadolinium Oxide (Gd2O3) as a gate dielectric/sensitive region in MOS based radiation sensors and to provide a detailed description of the frequency-dependent gamma irradiation response of a Gd2O3 MOS capacitor. The 254 nm thick-Gd2O3 films were deposited on p-type Si wafers by using RF magnetron sputtering. The radiation response of the Gd2O3 MOS capacitors was investigated by 6 degrees Co irradiation in the range of 0.5-70 Gy. The capacitance-voltage (C-V) curves shifted to a more positive potential with increasing radiation dose due to there being more trapped electrons than holes. The variation in the oxide trap charge density was found to be in the range of - 3.21 x 10(11) +/- 1.57 x 10(11) cm(-2) - - 1.70 x 10(12) +/- 8.33 x 10(10) cm(-2) at 100 kHz and - 2.26 x 10(11) +/- 1.02 x 10(10) cm(-2) - - 1.30 x 10(12) +/- 6.02 x 10(10) cm(-2) (70 Gy) at 1 MHz. The maximum variation in the interface trap charge density was in order of 10(11) cm(-2) at 1 MHz. The results indicate that the contribution of the oxide trap charge to radiation response of the Gd2O3 MOS capacitor is higher than that of the interface trap charges. The radiation sensitivities of the Gd2O3 MOS capacitor for 100 kHz and 1 MHz were determined as 59.2 +/- 2.9 mV/Gy and 62.7 +/- /9 mV/Gy, respectively. The percentage fading values (dose storage capability) measured in the time range of 25-145 min for 100 kHz varied from 2.2% to 11.4%.