Research On High Rectification Efficiency MOSFET For 2.45G Weak Energy Wireless Harvesting

As the most important part of the microwave wireless energy transmission system,the rectifier circuit converts the received RF energy into DC voltage to provide the required power for the subsequent system,and the energy conversion efficiency is an important indicator to evaluate the performance of microwave wireless energy transmission system.MOSFET has become one of the core rectifier device of the RF energy harvesting system because of its compatibility with CMOS ideal circuit technology.However,under the mainstream 2.45 GHz weak energy density RF signal input,the rectification efficiency of the MOSFET-based microwave RF wireless energy harvesting system is low.The paper aims to further improve the energy conversion efficiency of 2.45 GHz weak energy density wireless energy harvesting system,optimize the design of the core MOSFET devices and complete the construction of the rectifier circuit of the microwave wireless energy transmission system with high energy conversion efficiency.The results obtained are as follows:(1)Using the ADS simulation tool to compare and study the rectification output of two kinds of diode-connected MOS under different input signal frequency and amplitude.The simulation results show that the new diode-connected MOS can provide greater forward bias current and smaller reverse leakage current,which is obviously better than the typical diodeconnected MOS.And the new diode-connected MOS can be applied in both low and high frequency rectifier circuit,and is suitable for the microwave frequency band of 2.45 GHz.On this basis,the harmonic balance simulation of TSMC 0.18 μm process 1.8 V Native NMOS device with extremely low threshold voltage is carried out,and the influence of channel carrier mobility parameter in BSIM3 MOSFET model on the performance of rectifier circuit is determined.Finally,three effective approaches to improve the energy conversion efficiency of MOSFET are proposed,including new diode-connected mode with substrate biasing effect,reducing the threshold voltage,and improving the channel carrier mobility,which provides a theoretical basis for the subsequent design and optimization of high energy conversion efficiency MOSFET devices;(2)The physical properties of biaxial strained Si materials are studied,focusing on the establishment of strained Si/(001)Si Ge conduction band and valence band structure models,intrinsic carrier concentration model,and strained Si NMOS inversion layer mobility model.Finally,a quantitative model of carrier mobility in the biaxial strained Si NMOS inversion layer is given,and the conclusions can provide a theoretical basis for further research and design of biaxial strained Si surface channel MOS devices;(3)According to the requirements of the weak energy density wireless energy harvesting system for MOSFET rectifier devices proposed in(1)and the MOSFET threshold voltage theory,simulations of Native NMOS and strained Si Native NMOS are performed.Silvaco simulation tool is used to adjust its geometric structure parameters and doping parameters,and simulate and analyze its transfer characteristic curve,output characteristic curve,and carrier distribution under the condition of zero bias.The results show that the Si based biaxial strain technology significantly improves the electron mobility in the channel of NMOS device.Compared with the bulk Si NMOS device,the current drive capability of the strained Si MOS device is greatly improved.Finally,the half wave rectifier circuit is simulated,and it has been found that the single-tube energy conversion efficiency is indeed optimized.Compared with the common TSMC 1.8 V Native NMOS,the single-tube energy conversion efficiency has been improved by 3.3% and 8.5% in the weak energy density region of-20 d Bm and-10 d Bm respectively.The research on the relationship between MOSFET device parameters and energy conversion efficiency and the design of strained Si Native NMOS devices using new diodeconnected mode in this paper can provide useful reference for solving the problem of low rectification efficiency of the 2.45 GHz weak energy density microwave wireless energy harvesting system.