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E-mode P-GaN/AlGaN/GaN heterostructure field-effect transistors (HFETs) of various sizes were fabricated, and their parasitic source resistance (RS) was measured. The measurement results showed that RS varied greatly with changing gate bias, and the degree of RS change also differed with the gate bias of different-sized device samples. Through theoretical analysis, it is found that polarization Coulomb field (PCF) scattering caused by the device process and gate bias can affect electron mobility ( μ GS ) in the gate-source region, which causes the variations in μ GS for different-sized devices and same-sized devices under different gate biases. When μ GS changes with the device size and gate bias, the RS will change accordingly. Our study is the first to discover the gate bias dependency of RS for E-mode P-GaN/AlGaN/GaN HFETs due to PCF scattering, which provides a new idea for further in-depth studies on the RS of E-mode P-GaN/AlGaN/GaN HFETs and device performance optimization. [ABSTRACT FROM AUTHOR]

Identically-sized AlGaN/GaN HFETs were fabricated on three AlGaN/GaN heterostructure with differing AlGaN barrier layer thicknesses of 15.5 nm, 19.3 nm and 24.7 nm. Based on polarization Coulomb field (PCF) scattering theory, additional polarization charges and electron mobility under the gate were calculated, and the relationship between AlGaN barrier layer thickness and P C F scattering in AlGaN/GaN H F E T s was determined. For the AlGaN/GaN H F E T s with a thicker AlGaN barrier layer, when the same gate bias was applied to the gate, the inverse piezoelectric effect (IPE) of the barrier layer was weaker, resulting in fewer additional polarization charges. The AlGaN/GaN H F E T s with a thicker AlGaN barrier layer also possessed a higher 2DEG sheet charge density, diminishing the P C F scattering intensity. It can be concluded that increasing the AlGaN barrier layer thickness reduces the IPE and raises the 2DEG sheet charge density, both of which decreases the PCF scattering intensity. The results of this study have guiding value toward the optimization of AlGaN/GaN HFETs materials and structures. • The relationship between AlGaN barrier layer thickness and polarization Coulomb field (PCF) scattering was determined. • Both of the reduce of additional polarization charges and the increase of the 2DEG density will weaken the PCF scattering. • PCF scattering intensity can be diminished by increasing the AlGaN barrier layer thickness. • The results of this study have guiding value toward the optimization of AlGaN/GaN HFETs materials and structures. [ABSTRACT FROM AUTHOR]

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.. • The influence mechanism of Al composition in AlGaN barrier layer on PCF scattering in AlGaN/GaN HFET has been clarified. • The increase of Al composition will result in the increase of the additional polarization charges and the 2DEG density. • The contribution of the additional polarization charges and 2DEG density to PCF scattering is opposite. • The PCF scattering increases or decreases with the increase of Al composition, depending on which above factors is dominant. [ABSTRACT FROM AUTHOR]