Influence of frequency and gamma irradiation on the electrical characteristics of Er.sub.2O.sub.3, Gd.sub.2O.sub.3, Yb.sub.2O.sub.3, and HfO.sub.2 MOS-based devices

The unique physical, chemical, and electronic properties of rare earth oxides have been of immense interest to replace SiO.sub.2 as a dielectric material in metal-oxide-semiconductor (MOS)-based sensors applications to accurately measure the radiation dosage and increase sensor sensitivities in as diverse applications as space radiation, nuclear physics, medical diagnostics, radiation cancer therapy, and personal dosimetry devices. Hence, the electrical characteristics of oxides prior to and after irradiation of MOS-based devices are needed since they are the backbone of the devices such as MOSFETs and ICs. In addition, an understanding of the behaviour of high-k dielectric oxides in an MOS configuration is necessary since the radiation-induced damage occurs in the bulk oxide film and/or near the oxide-semiconductor interface resulting in creation of lattice defects. Hence, MOS structures with the rare earth oxides of Er.sub.2O.sub.3, Gd.sub.2O.sub.3, Yb.sub.2O.sub.3, and a transition metal oxide of HfO.sub.2 were produced by RF magnetron sputtering to determine (a) the structure of the films, (b) dielectric constants, (c) capacitance versus voltage behaviour of Er.sub.2O.sub.3, Gd.sub.2O.sub.3, Yb.sub.2O.sub.3, and HfO.sub.2 prior to and after irradiation of the devices in the dose range of 0-76 Gy. The experimental results were analysed with a theoretical framework on the energy band diagram and the radiation effects on the electrical characteristics of the MOS capacitors. The characteristics of the devices were evaluated by using effective oxide charge density ( [Formula omitted]), variation in the oxide trapped charge density ( [Formula omitted]), and interface trapped charge density ( [Formula omitted]). In addition, barrier height ( [Formula omitted]), image force barrier lowering ( [Formula omitted]), acceptor concentration ( [Formula omitted]) were calculated before and after irradiation and examined the nature of interface states. The radiation responses of the Er.sub.2O.sub.3 and HfO.sub.2 MOS capacitors did not show a stable behaviour with an increase in radiation dose due to possible neutral electron trap centres. Contrary to expectations, we infer that more negative charges are trapped in Gd.sub.2O.sub.3-based device than positive charges with an increase in radiation dose. The C-V curves of the Yb.sub.2O.sub.3 MOS capacitor shifted in the same direction at both 100 kHz and 1 MHz, and as expected, positive charge traps in the structure are mor