Physical Modeling of Threshold Voltage Instability in GaN High‐Electron‐Mobility Transistors

Abstract

The transient heat conduction equation for the 2D electron gas layer in GaN high‐electron‐mobility transistors is developed. The Schottky barrier height and the conduction band offset seen by electrons in the 2D electron gas layer will be reduced due to self‐heating in the 2D electron gas of GaN high‐electron‐mobility transistors via quantum coupling. Such a reduction will lead to a shift in the threshold voltage. To address this issue, an analytical physical model of self‐heating in the 2D electron gas of a GaN high‐electron‐mobility transistor via quantum coupling impacts on its threshold voltage instability is proposed. The proposed model forecasts that the threshold voltage can have an exponentially dependent relation with the reciprocal of the recovery time after the stress voltage is released, as well as dependencies on the square of the drift velocity, the gate voltage, and the surrounding temperature. The experimentally observed threshold voltage shifts of GaN high‐electron‐mobility transistors confirm such dependent relationships predicted by the proposed physical model. This article provides evidence that the combination of self‐heating in the 2D electron gas layer and quantum coupling may be a possible physical origin of the threshold voltage instability in GaN high‐electron‐mobility transistors.