A Study Of 3mm InP HEMT Devie Small Signal Medel

With the development of Millimeter-wave in military and space areas, InP high electron mobility transistor (HEMT) are drawn many attention because it’s high electron mobility, high frequency, low noise and high power gain. In this dissertation, InP HEMT and it’s small-signal model was investigated. The main results are summarized as follows:Firstly, we dissicuss the principle of HEMT devices, and illustrate the dc and ac characteristics of devices. Introduce the traditional small-signal model of FET. According to the properties of HEMT devices, we modify the small-signal model, so it can better reflect the characteristics of device. Based on the traditional small-signal model, we add two resistances which presenter the gate leakage current. Because of those two resistances, we improves the accuracy of model.Second, from the extensional structure, we use TCAD simulation software to simulate the internal physical characteristics of HEMT device. We main compare the difference of energy band and the concentration of Two-dimensional electron gass. Then choose the excellent performance structure. T-shaped gate is successfully fabricated through optimizing the exposure conditions. Introduce the testing methods of dc and ac characteristics. The testing band is made by Cascade semi-automatic probe band and Agilent 8363 PNA vector network analyzer. Setting test parameter is by IC-CAP software. Use the technology of microelectronics of Chinese academy of sciences, the InP HEMT device shows excellent DC and AC characteristics, the trans-conductance is 1064mS/mm,fT=196.8GHz and fmax=456GHz.Finally, this dissertation introduce parameters extraction and small-signal model, focus on the different methods to extract parameters which include intrinsic and parasitic parameters. First, we extract the parasitic parameters. Using ADS2009 to calculate the testing values which from the IC-CAP. There are many different methods to extract parasitic parameters, in this dissertation, we select the proper algorithm and calculate the value by comparing different methods and explaining the advantages and disadvantages. The most difficult part is extracting the value of parasitic resistances. We use DC extraction combining COLD-FET method to extract parasitic resistances. Then, we extract intrinsic part of parameters. First, we test the S parameters and remove the influence of parasitic parameters, then, according to the optimized small-signal equivalent circuit, calculate the value of intrinsic parameters through Y parameters after embedded of device. Building small-signal model is extracted parameters and put them into small-signal equivalent circuit. We fitting the test results and small-signal model. From fitting, we find those two curves have nice fit which indicate that the method we use in this dissertation can represent the actual small signal performance of HEMT device.Generally speaking, in this dissertation, according to the actual HEMT device, the method of building small signal connects the process and physical parameters of the underlying device with the upper device performance expressed by S parameter. On the other side, we can improve the device process technology and has good guidance value for the design of device structure and high frequency application circuit.