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This paper presents high performance device results using an ultra-thin AlN/GaN structure on sapphire substrate with a 100-nm T-gate. Excellent dc and RF characteristics are reported, including an extrinsic transconductance of 500 mS/mm and an extrinsic ft/fmax(U) ratio of 78/111-GHz which is among the highest reported for AlN/GaN HFETs. Low gate leakage results are also presented despite the small barrier thickness and absence of a gate dielectric. Modeling of the small signal parameters is also discussed to gain an understanding of the limiting and contributing performance factors. [ABSTRACT FROM AUTHOR]

This letter presents transistor device results on ultrathin AlN/GaN high-electron mobility transistors grown on a sapphire substrate with high dc/RF performance, including low gate leakage and high transconductance. Devices with 80- and 180-nm T-gates are compared, which demonstrate drain-induced off -state gate leakage currents below \10^-6\ \A/mm and extrinsic transconductance gm \sim \500\ \mS/mm by utilizing a \sim2–3 nm amorphous oxide layer formed under the T-gate during processing. In addition, excellent dc results such as RC < \0.50\ \Omega \cdot \mm and pulsed IDS, \max \sim \1.75\ \A/mm are reported. Small-signal RF performance using an 80-nm T-gate achieved ft > \100 \ \GHz operation, which is among the best so far reported for AlN/GaN technology. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistors (HEMTs) with a polarized polyvinylidene difluoride (PVDF) film coated on the gate area exhibited significant changes in channel conductance upon exposure to different ambient pressures. The PVDF thin film was deposited on the gate region with an ink-jet plotter. Next, the PDVF film was polarized with an electrode located 2 mm above the PVDF film at a bias voltage of 10 kV and 70 °C. Variations in ambient pressure induced changes in the charge in the polarized PVDF, leading to a change in surface charges on the gate region of the HEMT. Changes in the gate charge were amplified through the modulation of the drain current in the HEMT. By reversing the polarity of the polarized PVDF film, the drain current dependence on the pressure could be reversed. Our results indicate that HEMTs have potential for use as pressure sensors. [ABSTRACT FROM AUTHOR]

Abstract: AlGaN/GaN high electron mobility transistors (HEMTs) functionalized with ZnO nanorods were used for sensing CO in the concentration range of 50–500ppm balanced with air at ambient and temperatures from 25 to 250°C. An increase of the HEMT drain current was observed for exposure to the CO-containing ambient. The sensing limitation was improved from 100ppm to 50ppm by increasing the sensor temperature from room temperature to 250°C. The sensing response was also enhanced from 0.09% to 0.34% by increasing the sensor temperature. Reliable and repeatable current changes with the introduction of a low CO concentration of 50ppm and also rapid response times of ∼40s and recovery times ∼15s were demonstrated. [Copyright &y& Elsevier]