Decreased trap density and lower current collapse in AlGaN/GaN HEMTs by adding a magnetron-sputtered AlN gate

Abstract

In this paper, AlN films grown by magnetron sputtering method have been proposed as the gate insulator layer of AlGaN/GaN high-electron-mobility-transistors (HEMTs) to decrease gate leakage current and suppress the interface trap. The effect of the temperature of substrate on the quality of AlN films have been investigated. By inserting the thin AlN film (35 nm) as a gate insulator layer, the on-state resistance of AlGaN/GaN HEMTs decrease from 11.1 Ω·mm to 10.3 Ω·mm @Vg = 0 V, the current collapse decreases from 16.6% to 3.2%, the gate leakage can be reduced from 1.2×10-1 A/mm to 4.4×10-6 A/mm @Vg = 2 V by five orders of magnitude, and the fast interface states disappear and the normal trap density decreases from 0.96-1.3×1013 cm-2eV-1 to 1.3-3.4×1012 cm-2eV-1, proving that magnetron-sputtered AlN is an effective way to improve the performance of GaN HEMTs.

An insight to current collapse in GaN HEMT and suppressing techniques

“…To simultaneously achieve low leakage and low CC for high voltage AlGaN/GaN HEMTs, an AlN/SiNx stack passivation structure offers a practical solution [47].This stack layer gives better CC suppression as compared to the one with single AlN layer [48]. Using magnetron sputtering method grown AlN films as a gate insulator in AlGaN/GaN HEMT also decreases trap density which further helped to decrease the on sate resistance, gate leakage and current collapse [49]. Passivation layer's properties like dielectric constant, dielectric length and thickness also have effect in current collapse phenomena of AlGaN/GaN HEMT [50].…”

Simulation and analysis of enhancement-mode AlGaN/GaN HEMT with P-I-N junction gate

“…In an attempt to increase the threshold voltage, thin barrier layer structures and high Mg doping concentrations are often considered, however, the low 2DEG concentration of the thin barriers and low electron mobility caused by the diffusion of Mg dopants, resulting in a large on-resistance [11][12][13]. In order to reduce the gate leakage current and enhance the device reliability, researchers have proposed many ways, such as plasma treatment [14], and dielectric layer insertion [15][16][17][18]. Although these approaches enhance the gate reliability, defects or interface states may be introduced during the process, leading to large threshold hysteresis, which in turn increases the switching losses of the circuit.…”