Search

• 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]

• 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]

In this study, a split-gate AlGaN/GaN heterostructure field-effect transistor with an auxiliary gate was fabricated. Through experiment and analysis, it was discovered that by applying a constant potential (usually 0 V or negative potential) to the auxiliary gate, a negative bias can be formed between the auxiliary gate and the channel. This consumes the two-dimensional electron gas in the channel, leading to significant improvements in the saturation characteristics of split-gate devices. By applying different potentials to the main gate and the auxiliary gate, a variety of device working modes can be obtained, and the threshold voltage can be altered across a large range. These advantages make split-gate devices with auxiliary gates more suitable for increasingly complex integrated circuit applications. [ABSTRACT FROM AUTHOR]