Mechanism of Nonuniform Damage Induced by Low-Energy Protons in GaAs MESFETs

In this article, depletion-mode gallium arsenide metal-semiconductor field-effect transistors (GaAs MESFETs) were irradiated by 170-keV protons at room temperature. The threshold voltage (V-TH) remained unchanged with a fluence up to 3.2 x 10(12) p/cm(2). However, the drain current (I-DS) was degraded to a large extent. In contrast, both V-TH and I-DS degraded after 1-MeV electron irradiation. Through the nonionizing energy loss (NIEL) analysis, it is found that low-energy protons hardly affect the gate-controlled region of the device. The displacement damage dose caused by protons in the ungated region was larger than that caused by electrons, which is the main reason for the I-DS degradation, while the gated region was the sensitive region that affects the VTH. In addition, the case of proton and electron irradiations were modeled by TCAD simulation. The nonuniform damage mechanism of low-energy protons was fully revealed by the distribution of the electric field in the space charge region and transfer curves. The harmfulness of this mechanism to the power device was also discussed. This work will further provide a reference for the response of other types of devices to low-energy particle irradiation in space.