In this paper, an accurate parasitic parameters extraction method based on full wave electromagnetic for 0.1 μm GaN high electron mobility transistors (HEMTs) smallsignal equivalent circuit up to 110 GHz is presented. To describe the distribution effects of HEMTs electrodes at extremely high frequency, a 2-stage distributed transmission line equivalent circuit model is also presented. To minimize the distribution effects, a shorter gate-width device, called partial transistor model, is used to extract the second stage (N = 2) parasitic capacitance before extracting the first stage (N = 1) parameters. An AlGaN/GaN HEMT with gate length of 0.1 μm is used for validation, and the experimental results show that good agreement has been achieved between measured and simulated scattering (S) parameters up to 110 GHz. KEYWORDSAlGaN/GaN HEMTs, high frequency distribution effects, parasitic parameter model | INTRODUCTIONGaN-based high electron mobility transistors (HEMTs) are one of the most attractive solid device for high-power and high-frequency microwave devices. 1 Accurate models 2-4 can promote the efficiency of circuit design and is essential to circuit designer. With the increasing operation frequency of GaN HEMT, characterization of GaN HEMTs up to W-band is highly attracted recently. [5][6][7] At extremely high frequency, much more parasitic parameters for transistor need to be considered to account for high-frequency effects. However, the complicated parasitic parameters network will dramatically increase the difficulty of parameters extraction. Most of the papers have to use optimization method, which have challenges like multivalues problem, nonphysical results, and difficult to separate the parasitic capacitance and intrinsic capacitance. 8 It is need the guessed starting values of the parasitic parameters and a family of scaling devices be available for measurement to get the optimal values for device by Sergio. 9 Zlatica 10 used artificial neural networks for constructing a temperature-dependent model representing the small-signal scattering (S-) parameters of a GaN HEMT over a wide bias range and a board frequency range, while this method need tremendous measured data and high computer configuration. In Jarndal and Kompa, 11 a new parasitic elements extraction method based on cold pinch-off conditions was developed. This method uses only a cold-parameter measurement for accurate determination of the parasitic elements. The main advantage of this method is that it gives reliable values for the parasitic elements of the device without need for additional measurements or separate test pattern. But it needs hard task, when there are much more parasitic parameters up 110 GHz. Giovanni 12 used a new and simple T-network composed by lumped elements for representing the investigated GaN HEMT under a forward "cold" condition, which takes into account the capacitive effects of S11 and S22. All extrinsic parasitic elements are evaluated under "cold-FET" conditions without forward biasing the gate terminal. 13...

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In this paper, the performance difference of AlGaN/GaN high-electron mobility transistors (HEMTs) with same epitaxial structure fabricated silicon carbide (SiC) and transferred to diamond substrate is examined based on the surface-potential (SP) model. The thermal resistances of these devices are extracted through finite element method (FEM) thermal analysis. Results show that GaN-ondiamond device has a lower thermal resistance than conventional GaN-on-SiC device, which demonstrates the thermal performance improvement of GaN-on-Diamond technology. By embedding thermal characteristic into carrier mobility in the conventional SP model, the effectiveness of model is validated through good agreement between simulation and measurements of DC and RF performance. Additionally, large-signal performance (output power P out , power added efficiency P AE and Gain) on these two similar devices are compared under identical bias and temperature conditions based on the improved SP model, making this work be effective for improving the process of GaN-on-Diamond HEMTs. The excellent performance of GaN materials including wide bandgap, high thermal conductivity, high electron saturation drift velocity makes it very suitable for the development of highfrequency, high-power microwave and millimeter-wave device and circuit applications.1,2 SiC material is presently a major choice to implement high-performance GaN HEMT due to its high thermal conductivity that is an order of magnitude greater than that of other materials such as sapphire. However, the heat dissipation issue appears more and more prominent with the development to direction of smaller size, greater output power and higher frequency. Therefore, to solve the degradation of device performance and reliability caused by heat dissipation, it is of utmost importance to reduce thermal resistance to get good thermal management. [3][4][5] Recently, GaN HEMT devices fabricated on diamond substrate (GaN-on-diamond) have been developed 6,7 due to its high thermal conductivity (2000 W/m · K) that is three to four times that of SiC. The application of diamond substrate can significantly reduce the temperature rise of device, which is expected to solve the performance degeneration under conditions of high bias and power drive. [8][9][10] Accurate device model, especially physical model, is essential for predicting device performance and guiding process development. This paper discusses the comparison result of performance between GaN HEMTs fabricated on SiC and diamond substrates based on the SP model. The paper is organized as follows. In Device structure and fabrication section, the structure and fabrication process of GaN-onDiamond HEMTs are described in detail. Then the 3D FEM model and SP model are described briefly in Thermal analysis setup and results section and SP model description for following performance verification and discussion in RF Performance verification section. Finally, Conclusion section is the conclusion. Device Structure and FabricationThe cross-section view o...

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