Characteristics Research Of RF LDMOS Power Transistor

With the rapid development of mobile communication technology, the demand for RF power devices are increasing dramatically, which put forward higher requirements for the performance of RF power devices. In order to achieve localization for RF power devices applied in the field of mobile communication base stations and radar and other applications, in this paper, the silicon RF Lateral Double Diffused metal-oxide-semiconductor(LDMOS) power devices will be researched.This paper studies the S-band RF power LDMOS FET characteristics and the purpose is to design a RF LDMOS FET with working voltage 32 V, operating frequency 2.9GHz, power density greater than 0.7W/mm, power gain greater than 10 dB. First, the device structure used in this paper: the W sinker of the device is introduced into the source of the P-type heavily doped substrate; the single Faraday shield structure can optimize the electric field drift region and reduce the gate-drain parasitic capacitance. Then, according to the design specifications, the device characteristic is simulated by Silvaco and the structural parameters are determined. To reduce the parasitic parameters of the device and improve the breakdown voltage, some improved structures are described. The cellular structural parameters: 70μm two-finger gate structure, the length of the drift region 2.8μm, Faraday shield 0.8μm. Test results show that threshold voltage 2.1V, breakdown voltage 71 V, power density 0.8W/mm, cutoff frequency 10.2GHz, highest oscillation frequency 28.7GHz.Since the RF circuit designers use the device model to simulate the design work, the last part of this paper the S-band RF LDMOS device model is established. Small signal model is based on the traditional field effect transistor model, and the gate and drain wiring parasitic capacitance are increased. The simulation results and test results of small-signal model fit better. Then, based on Angelov model, the large signal nonlinear source-drain current Ids and nonlinear capacitance Cgs and Cgd are modeled.