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The relationship between mobility and subthreshold swing (SS) of AlGaN/GaN HFETs was investigated at 10 and 20 V drain bias using the Monte Carlo method. We find that the polarization Coulomb field (PCF) scattering dominates the mobility at both 10 and 20 V drain bias. The channel carrier mobility is reduced as the gate bias becomes more negative, which reduces SS. The influence of mobility has not been considered in the 60 mV/dec rule, and PCF scattering is crucial for SS to be lower than 60 mV/dec in AlGaN/GaN HFETs. However, when the drain bias is 10 V, the CF scattering significantly diminishes SS. When the drain bias is 20 V, the SS barely decreases. Accordingly, a lower drain–source bias is needed to appropriately reduce SS. [ABSTRACT FROM AUTHOR]

In this study, a novel AlGaN/GaN heterostructure field-effect transistor based on open-gate technology was fabricated. Sample transistors of different structures and sizes were constructed. Through measurements, it was found that by changing the width of the opening, the threshold voltage of the device could be easily modulated across a larger range. The open-gate device had two working modes with different transconductance. When the gate-source voltage VGS ≤ − 4.5 V, only the open region was conductive, and a new working mechanism modulated the channel current. Corresponding theoretical analysis and calculations showed that its saturation mechanism was related to a virtual gate formed by electron injection onto the surface. Also, the gate-source voltage modulated the open channel current by changing the channel electron mobility through polarization Coulomb field scattering. When used as class-A voltage amplifiers, open-gate devices can achieve effective voltage amplification with very low power consumption. [ABSTRACT FROM AUTHOR]

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]

A physics-based model for the output current–voltage (I–V) characteristics of AlGaN/GaN HFETs is developed based on AlGaAs/GaAs HFETs. It is demonstrated that Polarization Coulomb Field (PCF) scattering greatly influences channel electron mobility. With different gate biases, channel electron mobility is varied by PCF scattering. Furthermore, a more negative gate bias and a lower ratio of l g / l s d (gate length/source-drain space) of the device causes the PCF scattering to have stronger influence on channel electron mobility. This work is the first to apply PCF scattering to a physics-based model for AlGaN/GaN HFETs with I–V characteristics and the results indicate that PCF scattering is essential for a physics-based model to identify I–V characteristics of AlGaN/GaN HFETs. [ABSTRACT FROM AUTHOR]