Study On The Characteristics Of GaAs Vacuum Channel Photocathode With Nanopore Structur

GaAs vacuum channel photocathode has great potential in the field of terahertz electron sources due to its advantages of high emission current density,low dark current and high stability.The method research accounts for vast majority,and theoretical researches were almost non-existent.In this context,based on the finite difference time domain method and the equivalent medium theory,this paper conducts simulation calculations on shapes of GaAs vacuum channel photocathode in-channel,shapes of anode and cathode,thickness of anode composition and voltage.Provides guidance on the preparation of photocathodes.First,the effect of nanopore structure on GaAs material is studied.Using the method of controlling variables,effects of four shapes of circle,square,regular triangle and regular hexagon on optical properties of GaAs material were calculated from three angles of nanohole depth,duty cycle and period.By comparing four properties of reflectance,transmittance,absorptivity and average absorptivity,optical properties of different shapes were compared,and the optimal shape was obtained as a circular nanohole array.The light absorption power per unit volume of GaAs emission layer before and after constructions of circular nanohole arrays was analyzed.Secondly,the effect of different anode and cathode shapes on this photocathode was studied.By changing the width of anode,optical properties of photocathodes before and after construction of circular nanohole arrays in channels are compared,and it is proved that nanohole arrays can enhance the optical properties of photocathodes.At the same time,the photocathode electron-hole pair generation rate,band gap,electron distribution,emission current,emission current density and quantum efficiency were compared before and after construction of nanohole arrays,which proved that nanohole structures also have effects of enhancing electrical properties,and compare to get the best anode width.In order to study influence of cathode shape on photocathode performance,cathode was also designed into a channel shape.the influence of different cathode widths on electrical properties of photocathode was simulated,and the optimal photocathode anode and cathode shapes were obtained by comparison.Finally,effects of cathode composition thickness and voltage on electrical properties of this photocathode were investigated.Anode is composed of an insulating layer and an electrode layer,thicknesses of which will affect the absorption of incident light and emission of electrons by the underlying GaAs emitting layer.Therefore,different thicknesses of insulating layers and electrode layers were combined,their electrical properties were studied,and the best thickness combination was obtained.In order to study effects of voltage on this photocathode,change voltage and check changes of electrical properties of this photocathode,and get the best voltage by comparison,and finally obtain the GaAs vacuum channel photocathode with strongest performance.