Identifying the Properties of Traps in GaN High-Electron-Mobility Transistors via Amplitude Analysis Based on the Voltage-Transient Method

Abstract

In this work, we developed the voltage-transient method to characterize the properties of traps in AlGaN/GaN high-electron-mobility transistors (HEMTs) in the OFF-state. By monitoring the drain voltage transients of the HEMTs at various temperatures, three types of trapping mechanism were identified: 1) buffer charge trapping, which occurred on a timescale of approximately 1 ms; 2) charge trapping in the AlGaN layer at the gate–drain edge with the energy level ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{a}$ </tex-math></inline-formula> ) of approximately 0.54 eV; and 3) surface charge trapping with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{a}$ </tex-math></inline-formula> of approximately 0.28 eV. In particular, we extracted accurate amplitudes for the first two trapping behaviors and studied the dependence of the trapping effect on the filling bias conditions. The results showed that the buffer charge trapping was primarily affected by the drain voltage, whereas the charge trapping on the drain side of the gate was affected by both the drain and gate voltages; these results were verified by drift-diffusion simulations. In addition, we observed the third trapping behavior, which was apparent in the measurement window beyond 308 K, thus demonstrating the advantages of our method for correctly and effectively monitoring the changes in the peaks in the time constant spectrum.