Effect of γ-ray irradiation on breakdown voltage, ideality factor, dark current and series resistance of GaAs p–i–n diode

Effect of 60Co γ-ray radiation with 1×1016 γ/cm2 fluence on the ideality factor, saturation current and series resistance for two separate junctions p–i and i–n of p–i–n diode are studied by using temperature dependent current–voltage measurements and β model analysis. After γ-ray irradiation, the resistance of p–i–n diode increases from 858 to 2789 Ω. This is due to the fact that unintentional impurities (mainly carbon) present in the i-region change their positions from Gallium to Arsenic sites and subsequently transform them to the acceptor like states. The dark and saturation current decrease following the γ-ray irradiation because of the reduced electron mobility and the compensation of majority carriers by the acceptor like trap states. In addition, the ideality factor of p–i junction decreases from 1.5 to 1.2 while for the i–n junction it increases from 7.2 to 8 after irradiation at 300 K. The ideality factor for the second junction is enhanced due to the increased recombination probability of carriers at the trap centers in the intrinsic region. Positive temperature coefficient of the breakdown voltage confirms that the avalanche multiplication process is responsible for the junction breakdown. Further, the breakdown voltage increases after the irradiation because of the scattering of charge carriers from the radiation induced defects.