Analysis of Leakage Current Mechanism for Ni/Au Schottky Contact on InAlGaN/GaN HEMT

The gate leakage mechanism for InAlGaN/GaN high electron mobility transistors (HEMTs) is systematically studied using temperature‐dependent gate current–voltage characteristics. The electric field across the barrier layer is calculated through the extracted polarization charge and dielectric constant of the InAlGaN/GaN HEMT. The gate current of the InAlGaN/GaN HEMT is analyzed by fitting the experimental data using Themionic Emission (TE), Poole–Frenkel (PF), and Fowler–Nordheim (FN) tunneling. The results show that 1) reverse leakage current in the thin InAlGaN barrier layer is dominated by FN tunneling due to triangular barrier formation; 2) for thicker barrier layer, the reverse leakage current at low electric field (<2.23 MV cm−1) is dominated by PF emission; 3) at high electric field near the threshold voltage the FN tunneling dominates. Extraction of effective barrier height by fitting the experimental data with models leads to the suggestion for the improvement of the device leakage current. The gate leakage mechanism for InAlGaN/AlN/GaN HEMTs SBD with different barrier layer thickness is studied using current–voltage–temperature characteristics. As seen in the figure, at room temperature devices with thicker barrier layer has a higher leakage current in comparison to that of the thinner barrier layer. The possible mechanism is investigated and discussed systematically.