High Rectification Efficiency Direct Band Gap Ge_1-xSn_x Schottky Diode For Microwave Wireless Energy Transmission System

The microwave wireless energy transmission system(MWPT)consists of two parts:the transmitting end and the receiving end.The receiving end includes:a receiving antenna,a rectifier circuit and an impedance matching circuit.Because of the long-distance transmission,the microwave wireless energy transmission system has great application potential.Energy conversion efficiency is an important indicator for evaluating the performance of microwave wireless energy transmission systems.The overall efficiency can be improved by improving the conversion efficiency of different components of the system.For this reason,this paper designs the Schottky diode,the core component of the rectifier circuit at the receiving end,and optimizes the physical parameters of the material of the device,aiming to improve the energy conversion efficiency of the MWPT system.At present,Ge-based Schottky diodes are widely used in the market.The addition of>8%of the Sn component to Ge can alloy Ge and become a direct band gap semiconductor.The electron mobility of the direct band gap Ge_1-xSn_xalloy is 2 to 3 times that of Ge.Therefore,in recent years,the use of direct band gap Ge_1-xSn_xalloy to prepare Schottky diodes has attracted much attention.The paper mainly conducts research according to the following parts:1.Studies have shown that reducing the series resistance of Schottky diodes can effectively improve the rectification efficiency of the rectifier circuit.The series resistance is closely related to the mobility of carriers in the device,the device simulation of the DR-Ge_1-xSn_xalloy also requires a mobility value.Therefore,this paper firstly based on the k·p perturbation theory,based on the study of DR-Ge_1-xSn_xenergy band E-k relationship,and calculated the effective mass of the electrons of each crystal orientation group according to the energy band structure model,and established the DR-Ge_1-xSn_xcarrier migration quantitative analytical model of the rate,and the results of the energy band structure and mobility model were verified through PL spectrum and Monto Cano simulation.2.The device simulation of DR-Ge_1-xSn_xSchottky diode requires a work function value.At present,no scholar has reported the work function of DR-Ge_1-xSn_xalloy.For this reason,the CASTEP module based on Material Studio software simulates and analyzes the work function of DR-Ge_1-xSn_xalloys(x=0,0.09,0.10,0.125)with different Sn compositions along different crystal planes.Finally,the work function value of 4.132ev of the DR-Ge_1-xSn_xalloy with 10%Sn composition along the(100)crystal plane was selected as the data for subsequent Silvaco device simulation.At the same time,by comparing the work function value of Schottky contact formed by different metals,W was selected as the metal material for preparing Schottky junction with DR-Ge_1-xSn_xalloy.3.Based on the previously simulated DR-Ge_1-xSn_xalloy carrier mobility results and work function values,a Silvaco simulation tool was used to design a vertical structure DR-Ge_1-xSn_xSchottky diode.Using Cadence's Model Editor software to extract the Spice parameters of the simulated device,the results show that:compared with the traditional Ge Schottky diode,the series resistance of the new DR-Ge_0.9Sn_0.1Schottky diode designed in this article is significantly reduced.In order to further verify the change of energy conversion efficiency,a single-tube series rectifier circuit was built in the ADS software.The results show that:under the condition of frequency 2.45GHz and input energy density of 21.5d Bm,the single tube rectification efficiency of DR-Ge_0.9Sn_0.1Schottky diode can reach 75.4%,which is higher than the common HSMS-2820 Ge Schottky diode rectification efficiency 6.5%.In order to further optimize the circuit while considering the needs of practical applications,the Smith chart impedance matching circuit with series inductors and parallel capacitors is added to the original circuit.The results show that:the best rectification efficiency of 80.8%can be obtained at input power Pin=14.5 d Bm.In summary,the vertical structure DR-Ge_1-xSn_xSchottky diode designed in this paper is expected to provide a reference for the research of microwave wireless energy transmission system rectification output efficiency.