Radiation Response and Reliability of High Speed AlGaN/GaN HEMTs

Abstract

In recent years, GaN-based high-electron-mobility-transistors (HEMT) have demonstrated excellent high power and high frequency performance compared with counterparts based on other materials. Although AlGaN/GaN HEMTs are of great interest owing to the large band gap of GaN (3.4 eV), high breakdown field (~3.1 MV/cm), high saturation electron velocity (~2.5 × 107 cm/s) and the presence of a high-mobility two-dimensional electron gas (2DEG) at the hetero-interface, the reliability of devices can be limited by a number of factors, impeding the way to commercialization. GaN HEMTs have demonstrated very good radiation tolerance. In this work, the radiation response and reliability issues of AlGaN/GaN HEMTs grown using molecular beam epitaxy (MBE) are studied. Devices are subjected to 1.8 MeV proton irradiation and/or voltage stress are characterized via DC and RF measurements. Low frequency 1/f noise measurements are employed to help understand the defects that affect the reliability and radiation response of AlGaN/GaN HEMTs, and density functional theory (DFT) calculation is used to identify possible defect candidates. The temperature-dependent noise spectra show changes in defect distributions. Hydrogenated ON defects, Fe complexes and VGa-VN-Hx divacancies are some of the dominating defects limiting the device radiation response and reliability. The results of combined high field and radiation effects provide better insight into device response in practical space applications.