Abstract-The effect of gate leakage on the noise figure of AlGaN/GaN high electron mobility transistor (HEMTs) is explored. It is shown that these devices have a sizable amount of gate leakage that cannot be ignored when measuring their noise performance. Measurements across a single sample have more than 1 dB of variation in minimum noise figure. We will show this variation is because of gate leakage. A modified van der Ziel model is used to predict this large variation and allows easy noise figure prediction of HEMT and MESFET devices.Index Terms-AlGaN, GaN, gate leakage, high electron mobility transistor (HEMT), noise figure, van der Ziel.

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In this paper, the structure and processing of AlGaN/GaN high electron mobility transistors have been optimized for maximum small signal gain at high frequencies. The effect of the gate resistance, gate-to-drain capacitance and output conductance on the power gain cut-off frequency, f max , of the devices has been experimentally studied. The reduction of the gate width allowed a 4-fold decrease in gate resistance which resulted in almost a 100% increase in f max . To minimize C gd , Γ-shape gates have been processed instead of the conventional T-shape submicron gates. Finally, to reduce the output conductance, the confinement of the 2-dimensional electron gas was increased by using an ultra-thin InGaN layer below the GaN channel. This InGaN back-barrier caused a 2-fold improvement in output conductance which allowed a 20% increase in f max . By optimizing all these parameters, AlGaN/GaN transistors with a record f max of 230 GHz were obtained.

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Abstract-A C-band low-noise amplifier (LNA) is designed and fabricated using GAN HEMT power devices. The one-stage amplifier has a measured noise figure of 1.6 dB at 6 GHz, with an associated gain of 10.9 dB and IIP3 of 13 dBm. it also exhibits broadband operation from 4-8 GHz with noise figure less than 1.9 dB. The circuit can endure up to 31 dBm power from the input port. Compared to circuits based on other material and technology, the circuit shows comparable noise figure with improved dynamic range and survivability.Index Terms-GaN, high electron-mobility transistor (HEMT), high linearity, low-noise amplifier (LNA).