Effects of 60Co γ-ray irradiation on the electrical characteristics of Au/n-GaAs (MS) structures

In order to interpret the effect of 60Co γ-ray radiation dose on the electrical characteristics of metal-semiconductor (Au/n-GaAs) Schottky barrier diodes (SBDs), these devices were stressed with a zero bias during 60Co γ-ray source irradiation with the dose rate 2.12 kGy h−1 and the total dose range was 0-500 kGy at room temperature. Experimental results show that γ-irradiation induces an increase in the barrier height Φb(C-V) obtained from reverse-bias C-V measurements, whereas barrier height Φb(I-V) obtained from forward-bias I-V measurements remained essentially constant. This negligible change of Φb(I-V) is attributed to the low barrier height in regions associated with the surface termination of dislocations. The experimental I-V and C-V characteristics prove that there is a reaction for extra recombination centers in case of SBDs exposed to γ-ray radiation. Also, the ideality factor n and donor concentration decrease with increasing dose rate. Both I-V and C-V characteristics of the Schottky diode indicate that the total dose radiation hardness of GaAs devices may be limited by the susceptibility of the Au-GaAs interface to radiation-induced damage. The density of interface states NSS distribution profiles as a function ECC-ESS for each dose rate was extracted from the forward-bias I-V characteristics taking into account the bias dependence of the effective barrier height Φe at room temperature. NSS decreases with increasing dose rate and above 250 kGy it remains constant. Such a behavior of NSS is attributed to the existence of the native insulator layer between the metal and semiconductor that passivates the surface of semiconductor, and thus the increase of the NSS.