Comparison of module structure of wideband response GaAs photocathode grown by MBE and MOCVD

In order to compare the structures of GaAs photocathodes grown by molecular beam epitaxy (MBE) and metal-organic chemical vapour deposition (MOCVD), four wideband response exponential doping photocathodes were prepared. Theft reflectivity and transmittivity were measured by the spectrophotometer, and three thin layer thicknesses were fitted based on the matrix theory in Thin-film Optics. The comparison of the results indicated that for the GaAs photocathode grown by MBE, only one amendatory layer with the low Al component should be added between the Ga1-xAlxAs window layer and the GaAs active layer in order to the higher fitting accuracy. Opposite occurs for the MOCVD samples. In the case of accurately controlling the layered doping concentration, the material grown by MBE is the optimal, while that grown by MOCVD is suit for the exponential doping situation. These results are available for the material growth and the module preparation of the varied doping transmission-mode GaAs photocathodes. (C) 2014 Elsevier B.V. All rights reserved.