Investigations of Performances in RF GaN MIS-HEMTs and T-gate Schottky HEMTs with Leakage Current Analysis Using Emission Microscopy

Traditionally, Schottky HEMT structures are commonly used in Gallium Nitride (GaN) devices, but Metal-Insulator-Semiconductor (MIS)-HEMT structures have gained attention for their ability to decrease gate leakage current. In this work, we produced AIGaN/GaN <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MIS-HEMTs</tex> and Schottky HEMTs with a 15-nm in-situ SiN layer. The gate leakage current was effectively suppressed with the assistance of the insulator beneath the gate metal, and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MIS-HEMTs</tex> exhibit improved RF performances <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(fT / f MAX=89.95 / 144.95 GHz )</tex> compared to Schottky HEMTs <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(fT / f MAX=45.75 / 135.3 GHz )</tex> . However, an unexpected increase in device leakage current was observed during off-state drain breakdown analysis. Through emission microscopy (EMMI), we confirmed the presence of surface leakage between the gate-to-drain region via the in-situ SiN layer, which served as the leakage path and caused high leakage current under high drain voltage bias.