Fibre-optic plate bonded Al/sub 0.3/Ga/sub 0.7/As/GaAs transmission photocathode

An AlAs/GaAs/Al/sub 0.3/Ga/sub 0.7/As heterostructure on a GaAs substrate has been directly bonded on a fiber-optic plate for the first attempt of the 3rd generation transmission photocathode. The substrate is removed mechanically and etched chemically, utilizing high etching selectivities of GaAs and AlAs in potassium citrate/citric acid. The bonding strength between fiber optic and GaAs wafer exceeds 5.7 MPa without annealing, the final GaAs/Al/sub 0.3/Ga/sub 0.7/As structure on the fiber optic allows large dimension (1 cm /spl times/ 1 cm), thin (2 /spl mu/m) and uniform film thickness, and good transmission performance.