Proton irradiation effects on GaAs FET´s

Irradiation of 15 MeV protons on 1 µm-gate low noise GaAs FETs (MESFETs) with 2 × 10¹⁷cm^-3nominal channel doping is investigated. It is shown that a proton fluence around 1 × 10¹³cm^-2causes a detectable change in the saturation drain current IDSS, transconductance Gmand noise figure NF of the MESFET. After irradiation of 1 × 10¹⁴cm^-2protons or more, the devices do not function. This proton radiation sensitivity of MESFETs is about 100 times greater than reported hitherto neutron radiation sensitivity. Degradation behavior of IDSSand Gmhas been analyzed according to Shockley´s model and it is concluded that proton-induced MESFET degradation is mainly due to carrier removal and mobility reduction. NF behavior is analyzed based on Pucel´s theory. The discrepancy between the theoretical analysis and the experimental results for NF is partly explained by proton-induced change in the carrier concentration profile in the vicinity of the epi-buffer interface.