Gate Leakage Mechanisms in AlGaN/GaN and AlInN/GaN HEMTs: Comparison and Modeling

The gate leakage mechanisms in AlInN/GaN and AlGaN/GaN high electron mobility transistors (HEMTs) are compared using temperature-dependent gate current-voltage (I_G-V_G) characteristics. The reverse bias gate current of AlInN/GaN HEMTs is decomposed into three distinct components, which are thermionic emission (TE), Poole-Frenkel (PF) emission, and Fowler-Nordheim (FN) tunneling. The electric field across the barrier in AlGaN/GaN HEMTs is not sufficient to support FN tunneling. Hence, only TE and PF emission is observed in AlGaN/GaN HEMTs. In both sets of devices, however, an additional trap-assisted tunneling component of current is observed at low reverse bias. A model to describe the experimental I_G-V_G characteristics is proposed and the procedure to extract the associated parameters is described. The model follows the experimental gate leakage current closely over a wide range of bias and temperature for both AlGaN/GaN and AlInN/GaN HEMTs.