| The AlGaN/GaN high electron mobility transistors (HEMTs) have great potential in microwave and power applications due to its high power, high frequency and high temperature characteristics. The successful system level design of microwave circuits requires accurate device modeling, so small-signal and large-signal equivalent circuit model play an important role.Small-signal modeling of AlGaN/GaN HEMTs have been studied in many literatures. However, it is still difficult to obtain precise agreement between simulation and measurement result in a wide-band frequency range (specially for higher than40GHz), because when AlGaN/GaN HEMT operates above40GHz, the coplanar waveguide (CPW) effect is obviously. In this work, CPW capacitances (CCPW) were considered in the small-signal equivalent circuit of AlGaN/GaN HEMT. Add gate differential resistance Rfs and Rfd to reflect the device gate leakage current.When extract the parasitic resistance, the gate voltage is positively biased, gate differential resistance can not be ignored. AlGaN/GaN HEMTs operating frequency is very high,2DEG channel is equivalent to a section of transmission line and the distributed effects can not be ignored. On the basis of the traditional small-signal equivalent circuit model parameter extraction algorithm, the effects of channel resistance and gate leakage current are eliminated by linear interpolation for cold Z-parameters under different gate bias. Then, de-embed the effects of parasitic, the intrinsic values can be obtained. Analysis show that, in the200MHz to40GHz frequency range, S-parameters of the simulation results and measured data are in good agreement.Thereby, a large-signal equivalent circuit model is established and applied to the device. The model includes voltage-controlled current source and bias-dependent capacitance model element. The drain current equation accurately models the Ids over a large range of biases. An improved C-V model is introduced that accurately present the C-V characteristics. |
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