Electrical Characterization of Carbon Monoxide Sensitive High Temperature Sensor Diode Based on Catalytic Metal Gate-Insulator-Silicon Carbide Structure

Field-effect gas sensors based on catalytic metal-insulator-silicon carbide (MISiC) devices are investigated. For the evaluation of the barrier height, the temperature dependence of the current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of MISiC Schottky diodes were investigated in CO and O-2 atmospheres. Four methods were used to evaluate how a change in gas ambient influences the barrier height of the diode: a change of the intersection current at zero voltage in the forward direction of the I-V curve, a change of the temperature dependence in the forward direction and the reverse direction, respectively, of the curve, and a change of the intersection voltage of 1/C-2 versus plot. The four methods gave similar changes in the barrier height for the device in 8000 ppm CO and 4000 ppm O-2. The values of barrier height obtained from the I-V curves were here normalized by the ideality factor calculated from I-V measurements. The correlation between the barrier height change obtained from the and the C-V measurements, respectively, is discussed regarding the ideality factor. It is proposed that absolute value of the barrier height under flat-band condition is the most important for the evaluation of the barrier height. In the mixture of CO and O-2, the change of barrier height obtained from the C-V curve had roughly the same values as that from the I-V curve when normalized by the ideality factors.