Analysis of the Effects of High-Energy Electron Irradiation of GaN High-Electron-Mobility Transistors Using the Voltage-Transient Method

Abstract

The effects of high-energy (1 MeV) electron irradiation on the electrical and trapping properties of AlGaN/GaN high-electron-mobility transistors (HEMTs) are investigated systematically. When the irradiation fluence increases from 5 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to 1 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the drain-source current also increases and the threshold voltage shifts toward the negative direction. A Raman spectroscopy study shows that electron irradiation induces strain relaxation in the HEMT, which results in an improvement in the device's electrical characteristics. In particular, three traps in the device are identified using the voltage-transient method and the trapping effects in the HEMT are investigated after the final irradiation. When compared with the transient voltages during the pristine stage, the absolute amplitudes of the three traps in the device decrease after irradiation, which indicates a reduction in the density of the traps. Furthermore, it is proposed that the time constants of the three traps increase while the energy levels remain unchanged, which is ascribed to the strain relaxation and the structural ordering of the defects after electron irradiation. The observed changes in the trapping behaviors are consistent with the improvement in the electrical properties of the device and the shift in the Raman spectra.