Research On Emitting Layer Preparation Of GaSb Photocathode By MOCVD

In this paper,Ga Sb material in group III-V which GaAs is also belong to is researched by analyzing and studying the theory of low-light-level night vision photocathode and the characterization of its parameters.MOCVD technology is used to fabricate the GaSb material into the non-activated reflective photocathode emission layer.During the preparation process,the reaction temperature T and MO source V/III are selected as parametric variable,and the influence of different process parameters on the epitaxial quality of GaSb emissive layer during growth is studied by means of XRD and SEM,and optimized parameter combination of GaSb emissive thin film epitaxial growth was found.Next,GaSb emissive thin films with different doping structures were fabricated by homogenization and gradient doping according to experiment design,and their preparation quality and design parameters were verified by Hall test,SEM and AFM.Finally,the GaSb emissive layer with different doping structure was tested by photovoltage spectroscopy to test the spectral response range and compare the influence of different doping structures on the photoelectric properties,so as to explore whether the GaSb material has the capability of preparing high-performance low-light night-vision photocathode,which can provide theoretical support for the subsequent GaSb photocathode activation experiment and the parameter simulation and preparation process of the transmission GaSb photocathode.The experimental results show that T = 510℃,P = 100 mbar and V / III = 2 are the optimum parameter combination for the preparation of GaSb emissive layer thin films.SEM and AFM tests show that the GaSb emissive layer samples prepared by this parameter combination have surfaces close to the mirror surface.The height variation does not exceed 5.3 nm within scope of 1μmⅹ1μm.Surface photovoltage spectroscopy test shows that the wavelength response of GaSb emissive layer is about 1.7μm and has been extended to the mid-infrared band.GaSb material have the potential to be applied to preparation of new red-extended photocathode.In the selected doping concentration and thickness range,the surface photovoltage increases with the increase of the thickness,decreases with the increase of doping concentration.The gradient doping structure is more conducive to the transport of the photogenerated electrons to the surface than the homogeneous doping structure.