Photoelectron Emission Characteristics Of GaSb Photocathode

As one of the key components of photocathode-based photodetectors,one of the important research directions of photocathodes is how to extend their long-wave response to enhance the detection performance of the photodetector in the near-infrared region.Under the background of this research,this paper proposes The material represents GaSb as the material of the photocathode,material parameters of the GaSb photocathode surrounding,photocathode surface model,photoemissive process,heterojunction bias calculation,quantum efficiency theoretical model,structural design of the cathode material,preparation process and Photoelectric emission performance evaluation and other aspects of the study.According to the empirical formulae of Coy-Thomas et al.,the optical absorption coefficients of GaSb materials,the diffusion parameters of minority carriers,etc.,which have important effects on the photoemissive properties of GaSb photocathodes,are simulated.This provides an important reference for the structural parameters design of GaSb photocathodes.Based on Spicer's photo-emission three-step model,the physical process of photo-emission of GaSb photocathode was analyzed to provide a theoretical basis for the design of GaSb photocathode structure;the GaSb photocathode absorption layer and emitter heterojunction band structure were simulated.It is concluded that the bias voltage of 10×10V can well be eliminated when the doping concentration of the emitter layer is 1×10¹⁶cm^-3,the doping concentration of the absorber layer is 1×10¹⁷cm^-3,and the thickness of the emitter layer is 0.5?m.GaSb/p-GaAs barriers of gallium arsenide heterojunctions;based on several physical processes of photoemission of GaSb photocathodes,stepwise solution of one-dimensional minority subcontinuum equations and different boundary condition constraints,deducing GaSb photocathode quantum efficiency formulas The influence of various parameters in the formula on the photoemissive performance of the cathode is analyzed,and the optimized range of values for each cathode structure parameter is given.The absorption layer is doped Concentration of less than 1×10¹⁷cm^-3,the doping concentration of the emitter layer is 1×10¹⁶cm^-3,emitter layer thickness greater than 0.5microns.From the MOCVD growth process control theory,the influence of various parameters in the growth process on the growth of gallium antimonide epitaxial layer was analyzed.Considering the performance requirements of the photochemical cathode of antimony telluride,according to the MOCVD epitaxial growth theory,suitable growth conditions were selected.The GaSb epitaxial layer was prepared;the surface morphology and crystal quality of the GaSb epitaxial layer sample were measured by metallographic microscopy,SEM,and XRD,and a set of optimized growth conditions of the GaSb epitaxial layer were obtained by comparing the test results.A high-quality zinc-doped heavily doped GaSb epitaxial layer was prepared.The peak height-to-peak height of the AFM test surface was 4.1 nm,and the XRD?rocking curve measured the full width at half maximum of 0.2647°?888.12 arc sec?.The surface photoelectron spectroscopy test was used.To characterize the photoemissive performance of the inactive GaSb epitaxial layer,the minority-particle diffusion length of the epitaxial layer sample was fitted based on the surface photovoltage spectrum test results,and compared with the simulated GaSb proton scattering length calculation results,the results showed that the two are highly matched.It is considered that the surface photovoltage spectrum test can effectively evaluate the photoelectric emission performance of the GaSb epitaxial layer.By solving the one-dimensional and small-dimension continuous equations and different boundaries,the surface photovoltage expressions of the doped GaSb surface are deduced,and GaSb epitaxial layers with different doping structures are designed and grown.The epitaxial layers of GaSb with different doping structures are studied by surface photovoltage tests.Photoelectric properties,combined with test conditions and simulation results,were used to design the photocathode structure of the photochemical cathode.