The effects of frequency and γ-irradiation on the dielectric properties of MIS type Schottky diodes

The effects of γ-irradiation on the dielectric properties of Al/SiO2/p–Si (MIS) Schottky diodes were investigated using capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics. Before irradiation, the C–V and G/ω–V characteristics were measured by applying a small ac signal of 50 mV amplitude and 100 Hz–1 MHz frequencies, while the dc voltage was swept from positive bias to negative bias for MIS Schottky diodes. Afterwards, the C–V and G/ω–V measurements carried out at various radiation doses and 1 MHz. The MIS Schottky diodes were exposed to a 60Co γ-radiation source at a dose of 2.12 kGy/h and the total dose range was from zero to 450 kGy. The dielectric constant (ε′), dielectric loss (ε″), loss tangent (tan δ) and ac electrical conductivity (σac) were calculated from the C–V and G/ω–V measurements and plotted as a function of frequency and radiation dose. Experimental results show that the ε′ and ε″ were found to decrease with increasing frequency while increase with increasing radiation dose. In addition, tan δ versus log f show a peak, which was not present in the tan δ versus radiation dose. Also, the σac is found to increase with increasing radiation dose. These changes were attributed to mobile charge carriers or dipolar molecules generated by structural changes in the irradiated samples.