The influence of Al composition in AlGaN barrier layer on polarization Coulomb field scattering in AlGaN/GaN heterostructure field-effect transistors

Abstract

ABSTRACT The AlGaN/GaN heterostructure field-effect transistors (HFETs) with the same size were fabricated on two AlGaN/GaN heterojunction materials with different Al composition. Based on the polarization Coulomb field (PCF) scattering theory model, the additional polarization charges and electron mobility are calculated. By analyzing the results, it is found that the increase of the Al composition in barrier layer will result in the increase of the additional polarization charges and the channel 2DEG density. Although HFETs with a higher Al composition in barrier layer have higher additional polarization charges, because of the higher density of 2DEG, the additional polarization charge has a weaker scattering effect on 2DEG, and the intensity of the PCF scattering is weaker. The contribution of additional polarization charges and 2DEG density to PCF scattering is opposite. The intensity of PCF scattering increases or decreases with the increase of Al composition, depending on which influence of the additional polarization charges and the 2DEG density is dominant.