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• A novel method to determine bias-dependent source and drain parasitic series resistances in AlGaN/GaN high electron mobility transistors has been proposed. • The physical mechanism that causes R s and R d to vary with bias voltage is studied. • The bias voltage can affect the magnitude of R s and R d by affecting the optical phonon temperature and the intensity of the inverse piezoelectric effect. The AlGaN/GaN high electron mobility transistors (HEMTs) with T-gate that suitable for high frequency applications were fabricated. A novel method to extract the bias-dependent source and drain parasitic series resistances (R s and R d) of AlGaN/GaN HEMTs is proposed. By analyzing the distributed capacitance and current generator network in the velocity saturated regions of the AlGaN/GaN HEMTs, a new restriction relationship between small-signal equivalent circuit elements is found. The R s and R d can be determined under active bias through wideband S-parameter measurements, which can better reflect the physical mechanism of AlGaN/GaN HEMTs under normal operation. The S-parameters and extrinsic transconductance calculated based the small-signal equivalent circuit element values extracted by the method proposed in this paper are very consistent with the experimental values, which reflects the accuracy of this element extraction method. In this paper, the physical mechanism that causes R s and R d to vary with bias voltage is also studied. This study has a deeper insight into the bias-dependence of R s and R d , which modifies the understanding for physical mechanisms of AlGaN/GaN HEMTs. The research results provide new ideas for establishing small-signal equivalent circuit models containing more physical effects and is of great significance to GaN-based integrated circuit design. [ABSTRACT FROM AUTHOR]

• Normally-off recessed gate AlGaN/GaN MIS-HEMTs with ALD-Al 2 O 3 gate dielectric stack was fabricated. • The effect mechanism of PCF scattering on electrical properties of normally-off recessed gate AlGaN/GaN MIS-HEMTs was studied and clarified. • For the region underneath the gate, the increase in V GS resulted in an increase in Δ ρ G and n 2 D E G , moreover, the effect of n 2 D E G for PCF scattering is more significant than Δ ρ G. • For the gate-source region and gate-drain region, the parasitic resistance changes with V GS owing to the effect of PCF scattering, moreover, the effect of PCF scattering on the R S _ C H is stronger than R D _ C H . • This study perfects the carrier transport model of normally-off recessed gate AlGaN/GaN MIS-HEMTs and provides a new theoretical foundation for the device of this type to improving the electron mobility and reducing parasitic resistance. In this study, normally-off recessed gate AlGaN/GaN MIS-HEMT with ALD-Al 2 O 3 gate dielectric stack was fabricated. The influence of polarization Coulomb field (PCF) scattering on electrical properties of normally-off recessed gate AlGaN/GaN MIS-HEMTs with ALD-Al 2 O 3 gate dielectric stack was studied. Based on the measured I-V data, the electrical parameters such as additional polarization charge (Δ ρ G), electron mobility (μ), gate-source (G-S) parasitic resistance (R S) and gate-drain (G-D) parasitic resistance (R D) were obtained by iterative calculation method. Through systematic analyzed of these results, it was found that the positive G-S voltage (V GS) induces tensile strain in the ultra-thin AlGaN barrier layer, which was AlGaN remaining after etching and existsed between the gate dielectric and the GaN channel, resulting in positive Δ ρ G under the gate. With the increase of V GS , the inverse piezoelectric effect in the ultra-thin AlGaN layer increases and the amount of Δ ρ G increases. At the same time, the positive V GS induces two-dimensional electron gas (2DEG) underneath the gate, which is also positively correlated with the V GS. Compared with Δ ρ G , the 2DEG density (n 2 D E G ) has a greater effect on the PCF scattering strength. We also found that the influence of PCF scattering on R S and R D is different, which is related to the difference between G-S distance and G-D distance. This study provides a new theoretical basis for normally-off recessed gate AlGaN/GaN MIS-HEMTs to improving μ and reducing parasitic resistance. [ABSTRACT FROM AUTHOR]

An InAlN/GaN MIS-HEMT with ZrO 2 gate dielectric layer and a Schottky-gate InAlN/GaN HEMT were fabricated. Subsequently, the influence of ZrO 2 gate dielectric layer on polarization Coulomb field (PCF) scattering in InAlN/GaN MIS-HEMT was studied. Compared with InAlN/GaN HEMT, the ZrO 2 gate dielectric layer in InAlN/GaN MIS-HEMT results in fewer additional polarization charge and higher two-dimensional electron gas density at the same gate-source voltage (V GS) conditions. Also, we established that both of these factors weaken PCF scattering intensity. However, the InAlN/GaN MIS-HEMT has a larger gate swing. Therefore, there is a smaller V GS was applied during regular operation of device. When the V GS is small, PCF scattering is the strongest scattering and play non-negligible impact in the size of total electron mobility. This study provides a new theoretical foundation for further enhancing the performance of InAlN/GaN MIS-HEMTs. • The influence of the ZrO 2 gate dielectric layer on PCF scattering in InAlN/GaN MIS-HEMTs was determined. • The ZrO 2 layer leads to fewer Δ ρ G and higher n 2 D E G at the same gate bias conditions, both of these factors weaken PCF scattering intensity. • When the gate bias is small, PCF scattering plays a dominant role in the magnitude of the total electron mobility. • The results of this study have providing a new theoretical basis for further enhancing performance of InAlN/GaN MIS-HEMTs. [ABSTRACT FROM AUTHOR]