The Study Of Dyakonov-Shur Instability Based On The Gated Cylindrical Field Effect Transistor

With the development of terahertz(THz)technology,terahertz waves have been applied to many fields,which has greatly promoted the research of terahertz devices,especially the research of terahertz source devices.In 1993,Dyakonov and Shur provided an instability theory in field effect transistors(FET),which made the FET to be a THz source.The theory shows that plasma waves can be excited in the channel of the FET because of special asymmetric boundary conditions.Subsequently,with the oscillation of the plasma wave,the oscillation frequency reaches THz range,and the THz electromagnetic wave can be radiated from the FET.The instability of plasma waves,in channel,is called Dyakonov-Shur instability(DS instability).Some experiments have shown that the THz wave are generated in FETs with DS instability.Some scientists have investigated the DS instability,but there are many physical problems that need to be solved.In general,most of the research are studied in traditional rectangular FETs.With the rapid development of science and technology,more new devices are being developed.Especially semiconductor technology has entered the nano age,and the quantum effects in nanometer devices cannot be ignored.It is important to investigate these device.And the main research contents and conclusions are as follows:(1)According to the DS instability theory,the two-dimensional(2D)hydrodynamic equations in a cylindrical coordinate system are used to investigate the DS instability in the gated cylindrical FET.The effects of channel radius and mode number on the oscillation frequency and the instability increment are analyzed.In the cylindrical FET,DS instability is a 2D problem,and plasma waves spirally propagate in the channel from source to drain.In this case,the asymmetric boundary condition needs to be rewritten,and another dimension boundary condition must be added to close the system.In addition to length of channel,a new device parameter,radius of channel,is introduced,and the spiral propagation of plasma waves results the influence of mode number.An adjustable THz source can be achieved by adjusting these device parameters.(2)Miniaturization and integration have become the main development trends of electronic devices.In nanometer FET,quantum effects have become particularly important and have an irreplaceable influence on FETs.The DS instability in nanometer cylindrical FET is studied by using quantum hydrodynamic equations in cylindrical coordinates system.In this case,not only the mode number and the radius of channel can affect the oscillation frequency and the instability increment,but the quantum effects and the electron temperature can also affect them.This research provides a theoretical basis for nanometer cylindrical FET THz source.The THz source can change the frequency by adjusting the device parameters.