The Research For Building A GaN HEMT Power Device Model And Design-kit

Gallium nitride （GaN） is developing rapidly as one of the third generationsemiconductor materials, comparing to the previous two generations of semiconductormaterials silicon （Si） and gallium arsenide （GaAs）, GaN has the characteristics of widebandgap, high electron saturation rate, high electron mobility, high breakdown voltage,good thermal conductivity and good stability. The GaN high electron mobility transistor（HEMT） has broad application in the prospects such as microwave communication,radar system, high power device with the characteristics of high working frequency,strong output power density, high radiation resistance, high temperature resistant. Thetraditional FET models can’t accurately simulate the characteristics of GaN HEMTbecause of its high frequency characteristics and the thermal effect, so it is extremelyimportant to establish an accurate GaN HEMT model. This paper focuses on themodeling technology of GaN HEMT and building a design-kit of GaN HEMT powerdevice.First of all, considering the high frequency effect of the distribution of capacitance,this paper adds three parasitic capacitances to represent interelectrode crosstalk betweenthe gate, source and drain based on the traditional FET small signal equivalent circuitmodel.Use the direct extraction method to extract the initial of the small-signalequivalent circuit, then use the full-band opimization to obtain all the values of thesmall-signal equivalent circuit. The improved small-signal equivalent circuit modelunder different bias,1-20GHz compared with the measured results of the S parameter,the amplitude relative error is less than5%and the absolute phase error is less than5°,so the improved model has higher accuracy and is an important foundation for theestablishment of large-signal equivalent circuit model.Then we add the thermal circuit to represent the device self-heating effect and thetemperature items to improve output characteristics combined with its significantself-heating characteristics based on the GaN HEMT traditional Angelov nonlineardrain-source current （Ids）. The improved model of Ids fits well with the measured results.And establish the gate-source, gate-drain capacitances expression with the imprcvements in the traditional Angelov nonlinear capacitance model. The large-signalequivalent circuit model embeded in ADS with the form of the symbol defined device（SDD）. At the same time we establish the temperature related large-signal modelcombined with the influence of temperature on the I-V output characteristic. Therelative error of the dc I-V of this model is less than8%with the V_ds from5V to30V,V_gsfrom0V to–V_p, temperature from25oC to175oC.At last, we establish the model of GaN passive components including inductor,capacitor, through-hole, microtrip line. The simulation S-parameter of the modelcompared with the electromagnetic simulation result has high consisitency, thenestablish the design-kit of GaN devices.