Effect of multilayer complex buffer layer structures on photoelectric performance of GaAs-based photocathodes

To enhance the photoemission capabilities of GaAs based photocathodes, two kinds of multilayer complex structures with respectively graded bandgap and distributed Bragg reflector in changing buffer layer have been proposed. In order to better study the different performance of the two photocathodes with complex structures, the experimental reflectivity and spectral response are measured. The theoretical optical properties of the multilayer GaAs based photocathode modules are calculated by matrix formula on the basis of thin-film optical principles, and some performance parameters on optical properties are analyzed by simulation. The results show that the photoelectric performance of the photocathodes with the two structures are quite different. The simulations show that the performance parameters have complicated effects on the optical properties. Different parameters are presented as the changes of peak and valley of the optical property curves, and they play different roles on the two structures. Meanwhile, the emission layer has a significant effect on the absorptivity values of the photocathode modules, which will obviously influence photoemission performance. Moreover, a best fit of the experimental reflectivity data can be achieved with the aid of the deduced optical properties model. The optical properties via calculation would make reasonable guidance for further investigation of these complex graded bandgap photoemitters.

Automated summary

Two kinds of complex structures for GaAs based photocathodes are proposed to enhance their photoemission capabilities. Experimental and simulated calculations are conducted to compare the optical properties of the two structures. The results show significant differences in photoelectric performance between the two photocathodes, with complex effects of different parameters on optical properties and a significant influence of the emission layer on absorptivity values.