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• The mechanism of enhanced for PCF scattering in AlN/GaN HFETs has been clarified. • A large number of additional polarization charges (Δ ρ G) are generated under the gate. • Δ ρ G will become saturated with the decrease in gate bias. • The decreases of 2DEG density will enhance the PCF scattering intensity. AlN/GaN heterostructure field-effect transistors (HFETs) was fabricated. Based on the polarization Coulomb field (PCF) scattering theory model, the additional polarization charges and mobility are obtained by iterative calculation method. By analyzing the results, it is found that (i) the electric field strength in the AlN barrier layer is large because it is ultrathin, and the piezoelectric tensor coefficient of AlN material is large; thus, the inverse piezoelectric effect is very strong. A large number of additional polarization charges are generated under the gate, which can generate a strong PCF scattering potential and enhance PCF scattering. What's more, the AlN barrier layer cannot be infinitely strained by the gate bias with the converse piezoelectric effect, and the additional polarization charges will become saturated with the decrease in gate bias. (ii) The AlN barrier layer of AlN/GaN HFETs is ultrathin, the two-dimensional electron gas (2DEG) density under the gate is quickly decreased by the gate bias, and, with the decrease in 2DEG density, PCF scattering is enhanced. [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]

In this work, two AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with different ratios of gate length (L G) to gate-drain distance (L GD) were used to compare the effects of ratio of L G to L GD on the source access resistance (R GS) at 300 K , 350 K , and 400 K. The results showed that the ratio of L G to L GD had a significant effect on R GS at the above-mentioned each temperature, which can be attributed to the polarization Coulomb field (PCF) scattering. In addition, the effects of the ratio of L G to L GD on R GS in the two AlGaN/AlN/GaN HFETs prepared in this work were different at different temperatures. This indicated that elevated-temperature performance of AlGaN/AlN/GaN HFETs can be improved by optimizing the ratio of L G to L GD based on PCF scattering. [Display omitted] • The effects of the ratio of L G to L GD on R GS in AlGaN/AlN/GaN HFETs are investigated at different temperatures. • It is found that the ratio of L G to L GD has a significant effect on R GS at each testing temperature. • PCF scattering is responsible for the effects of the ratio of L G to L GD on R GS. • R GS can be modulated by optimizing the ratio of L G to L GD based on PCF scattering. [ABSTRACT FROM AUTHOR]