Simulation of the Fowler–Nordheim tunneling current through the gate dielectric of AlGaN/AlN/GaN MIS-HEMT

Abstract

In metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) based on GaN, two main conduction mechanisms contribute to the gate leakage current. At low electric fields across the gate dielectric, the dominant mechanism is Poole–Frenkel emission. At sufficiently high electric fields, the gate leakage current is primarily governed by Fowler–Nordheim tunneling. The latter process is strongly dependent on the applied electric field and the dielectric properties, which makes it a critical factor in the design of the gate stack. In this paper, we estimated the Fowler–Nordheim tunneling current through the thin SiO2 gate dielectric of an AlGaN/AlN/GaN MIS-HEMT at low to medium reverse and forward gate-source biases. It is shown that the leakage current through ultrathin 2–4-nm SiO2 layers may cause electrical breakdown of the gate dielectric, when the device is biased at less than ±20 V.