Research On Structure Design And Preparation Of GaAs Wire-array Photocathode

The effective surface electron affinity of the negatively charged GaAs photocathode material is less than zero,indicating great improvements in its quantum efficiency.This photocathode material is a highly sensitive optoelectronic detection and photoemission material with wide use in the fields of micro-optical imaging and high-performance electronics.However,modern advancements in technology have increased requirements for better quantum efficiency and a wider spectral response range of the photocathode.Therefore,research on improving the performance of Negative Electron Affinity?NEA?GaAs photocathodes to meeting existing demands and expand their application scope is a worthwhile endeavor.Nanotechnology provides a direction for this field of research.Semiconductor micro/nanowire arrays are typical representatives of nanotechnology.When photons enter an array,absorption occurs.Photons that are not absorbed are absorbed by the photon capture effect.The radius of micro/nanowires is small and their lengths are short enough to allow photoelectrons to be transported to the surface of the micro/nanowires.This phenomenon is immensely beneficial to photoemission because it can overcome the limitations of traditional thin film materials in terms of electron transport.This paper describes the band structure,preparation technology,and photoelectric characteristics of GaAs micro/nanowire arrays.Research on photoemission theory and the preparation technology of Ga As array photocathodes is also presented.First,utilizing photoemission theory and quantum mechanics theory,this paper studies the surface transport characteristics of optoelectronics,the surface energy of GaAs micro/nanowire array photocathodes,and the surface tunneling effect.Using the finite difference method,the optical characteristics of GaAs nanowire array photocathodes are simulated,and reasonable parameter values affecting the performance of these photocathodes,such as angle of incident light and size and duty ratio of the arrays,are obtained.Second,the fabrication GaAs micro/nanowire arrays is explored.The reflectance and photoluminesecence?PL?spectra of these arrays with different diameters and shapes,as well as the structures of the GaAs thin films,are compared.The preparation method of moNo.dispersed SiO₂ microspheres is also studied.Self-assembly of non-densely stacked SiO₂microspheres is achieved on a gas-liquid surface.The target size of single-layer SiO₂microsphere films is obtained and used as a barrier layer on which engraving by inductively coupled plasma?ICP?etching is performed.The SiO₂ microspheres are used to modulate the nanowire diameter and duty cycle.The required GaAs nanowire arrays are then obtained through ICP etching.Third,the photocurrent responses of GaAs microarray photocathodes with different shapes are compared.Compared with circular GaAs microarrays,square GaAs microarrays demonstrate better spectral responses.In addition,the surface of GaAs nanowire arrays prepared by the colloidal crystal etching process is easily activated,and their quantum efficiency is 4.7 times that of GaAs film photocathodes.Fourth,the characteristic resolution of the graded doping and component AlGaAs/GaAs photocathodes is studied,and the factors influencing this resolution,such as such as AlGaAs thickness,GaAs thickness,and incident wavelength,are evaluated by establishing a theoretical model.The modulation transfer function?MTF?of the reflective photocathode is higher than that of the transmission photocathode,and the graded component structure is better than the graded doping structure for photocathode MTFs.The exponentially doped and linear component structure of the transmission photocathode and the linearly doped and linear component structure of the reflective photocathode show the highest MTF values among the devices studied.Finally,the photocurrent characteristics of the graded doped AlGaAs/GaAs nanowire device are explored.The dynamic mode of the scanning photocurrent of the low injection-graded doping and graded component AlGaAs/Ga As nanowire devices is first established by spectroscopy and then simulated.The simulation results enable analysis of the types of doping and components.