Study On Gate-modulated Gunn Oscillation Based On GaN-HEMT For Terahertz Applications

At present,the fifth-generation(5G)communication,hundreds of times faster than 4G,has begun commercial applications worldwide,but it may still not be able to meet the needs of emerging systems including the Internet of Things(Io T)in a decade.To meet the demand of beyond-5G and 6G technologies for communication systems,the higher frequency terahertz(THz)wave,as higher frequency electromagnetic waves,is extremely important for the future development of communication.In recent years,the study of terahertz radiation sources has become the focus of researchers from all over the world.Gallium nitride(GaN)materials stand out due to their large forbidden band width,high mobility and other advantages.The terahertz power devices based on GaN material have been widely used in military fields such as millimeter wave radar.As an excellent solid-state oscillator based on the negative resistance effect,the Gunn device has many advantages such as low energy consumption,high frequency,low noise,and high reliability,and has shown great application prospects in the field of terahertz.The gallium nitride-based high electron mobility transistor(GaN-HEMT)can reduce and fix the length of the "dead zone" because the gate can be used as the hot electron injection region in the channel,which improves the performance of the device.In recent years,there are more and more researchers are concerned about the Gunn effect in HEMT devices and hope to make a terahertz oscillation source.Based on the above research background,the GaN-based HEMT device with thin passivated field plate(FP)structure is deeply studied in theoretical and simulation,and the ability to induce Gunn oscillation is explored with its unique transverse electric field characteristics of "two peaks and one valley" channel.Firstly,it is found that the field intensity peak at the gate drain side can be used as a single nucleation point,and the self-excited oscillation frequency can be greatly changed by changing the electric field distribution of the grid voltage-modulated channel in a unique quenched domain number pattern.The effects of the thickness of the passivation layer and the length of the field plate on the oscillation frequency and the starting gate voltage under the same quenched domain pattern are also studied.Secondly,the device size and nucleation mechanism required to produce the double nucleation point oscillation are studied,and it is proved that the frequency modulation can be realized by changing the number of nucleation points with the appropriate size design,which provides a new idea for the gunn oscillation gate-controlled frequency modulation in three-port device.Then the gate-controllable Gunn oscillation with the field intensity peak on the drain side of the field plate as the single nucleation point is studied.The requirements on the device size are analyzed and the great differences between this mode and the field intensity peak on the drain side of the field plate as the single nucleation point are compared.Finally,the relationship between the length of the field plate and the thickness of the passivation layer required for the nucleation point formed by the two field strength peaks is summarized,and the differences between the FP-HEMT which can form electronic domains and the conventional field plate device are compared and analyzed.The reason why FPHEMT with Gunn oscillation has not been manufactured is analyzed.The characteristics of the above FP-HEMT are all caused by the electric field characteristics of the channel "two peaks and one valley".Compared with the Gunn effect in the groove barrier structure HEMT which has been reported,the Gunn oscillation of the FP-HEMT has a higher frequency and a wider range of frequency modulation.The unique quenching domain number mode and gate control nucleation point number in FP-HEMT are a new way of gate-controllable frequency modulation method,which is of great practical and research value.And because the field plate technology is mature and simple to manufacture,it can avoid the damage of the two-dimensional electron gas(2DEG)by etching.Therefore,the use of Gunn oscillation in the field plate structure GaN-based HEMT to fabricate the terahertz source has considerable advantages and Potential,will surely play a role in the field of terahertz technology in the future.