The Submicron GaAs PHEMT Device And Its Small Signal Modeling

The semiconductor device utilized the heterostructure has gain great achievements, since providing its concept in 1951. Comparing the homojunction, the heterostructure possesses high density and high mobility. These help the semiconductor device to work in microwave and millimeter-wave frequencies. So, since the Pseudomorphic HEMT (PHEMT) was invented in 1985 by Rosenberg and Ketterson respectively, the PHEMT technology was being pursued by every country. Passed several decades, the PHEMT devices have demonstrated great potential in military and commercial systems, including radar, communication, and automotive technologies, due to their high frequency, high power, and low noise characteristics. Based on the previous work, this paper is to research the low-noise PHEMT device. In order to gain superior PHEMT devices, it contains three parts.Firstly, the structure of the low-noise PHEMT device was designed. The PHEMT structure can be divided into two parts, which is perpendicular structure and horizontal structure. During the design of its perpendicular structure, the paper firstly analyzed its main parameters, according to the I-V characteristics of FET, and then numerical computed the relation between its layer structure and parameters by using the POSES software. During the deign of its horizontal structure, the paper qualitatively analyzed the effect of its layout, by utilizing the typical small-signal equivalent circuit. At last, according to the above results, we get the structure of PHEMT devices. Secondly, the fabrication process of the PHEMT device was studied. Based on the previous MESFET process, the paper provided its complete process, and analyzed these key fabrication steps. By measuring the PHEMT device with the dimension of 0.5μm*40μm*3, we got the following parameters: I_dss=186mA/mm, g_max=379mS/mm, f_T=25GHz, f_max=52GHz.Finally, the small-signal model of the PHEMT was developed. Thanks to direct-extraction methods, the small-signal modeling was written in ICCCAP software. By testing the FET with different structures and sizes, shows that the model can accurately described the FET's small-signal characteristics from 0.1 to 20GHz.