Density-Dependent Electron Transport and Precise Modeling of GaN HEMTs

TL;DR

This paper presents direct measurements of electron transport in GaN HEMTs, introduces a new velocity model based on optical phonon emission, and validates it through device simulations, enhancing understanding and modeling accuracy.

Contribution

It introduces a novel optical phonon emission-based electron velocity model for GaN and validates it with experimental data and device simulations.

Findings

Electron velocity increases with decreasing sheet charge density.

The new model accurately predicts density-dependent saturation velocity.

Simulations agree well with experimental measurements of GaN HEMT characteristics.

Abstract

We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors. Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 x 10^7 cm/s at a low sheet charge density of 7.8 x 10^11 cm-2. A new optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated LO phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.