The Impact of Non-Uniform Distribution of Radiation-Induced Defects on the Electrical Performance of AlGaN/GaN HEMTs

This study investigates AlGaN/GaN HEMTs irradiated with chlorine ions of varying energies, which introduces depth-dependent non-uniform defects beneath the gate electrode. By combining experimental and simulation methods, we systematically analyze three distinct degradation phenomena: non-uniform degradation in transfer characteristics, threshold voltage (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub>) shift saturation, and Peak transconductance (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G_M</i>) collapse. Through Current deep-level transient spectroscopy (I-DLTS), electrical performance measurement, and TCAD device simulation, along with band theory analysis, it is found that high fluence chlorine irradiation generates Fe<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ga</sub>-V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> defects (E<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>C</i></sub>-0.5 eV) in the GaN layer, inducing Fermi-level pinning at these trap states. The increased defect concentration causes interfacial band bending and reduces 2DEG density. Donor defect E1 near the AlGaN/GaN interface are identified as the primary contributor to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> shift saturation behavior. Additionally, V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub>-V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> (+1/+2) defects (E<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>C</i></sub>-0.77 eV) in the AlGaN barrier layer become activated when gate voltage exceeds a critical value, significantly enhancing electron capture from the conduction band. This spatially non-uniform trapping process leads to gate-voltage-dependent degradation of drain current (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub>) and ultimately results in the phenomenon of Peak <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G_M</i> collapse.