Cathodoluminescent spectroscopy and electric properties of MODFETs of AlxGa1−xN/GaN at impact of proton irradiation 1.8 MeV

The cathodoluminescent spectroscopy (CLS) in order to examine AlGaN/GaN modulation-doped field-effect transistors that display degraded source-drain current characteristics after 1.8-MeV proton irradiation, along with bulk heterojunctions of materials of field-effect transistor. For both cases, we have observed distinct changes in the spectral emission features due to decreased internal electric-field strength and new point defects within different layers of the device structure with the nanometer-scale depth resolution. These changes might be accounted for the degraded electrical characteristics. The degradation of Al-GaN/GaN high electron mobility transistors due to 1.8-MeV proton irradiation was measured at fluence up to 3·1014 cm-2. The devices have much higher mobility than AlGaN/GaN devices, but they possess high radiation tolerance, exhibiting little degradation at fluence up to 1011 cm-2. Decreased sheet carrier mobility due to the increased carrier scattering and the decreased sheet carrier density due to the carrier removal are primary damage mechanisms. The device degradation has been observed with the decrease in the maximum transconductance, the increase in the threshold voltage, and the decrease in the drain saturation current.