STUDY OF ASGA COLD MICROCATHODE TIPS AND PLATES FOR MICROWAVE APPLICATIONS

The field emission cathodes investigated in this paper are based on ti ps or wedges structures. Fabricated on a highly doped GaAs substrate, these devices give maximum current values of 100 mu A under low voltag e, both for tips and wedges. Two methods are used to Jit the I-V chara cteristics. The emission field uniformity seems to be improved in case of wedge structures, particularly after a << self-shaping >> period o f time. Although the geometry appears theoretically less favourable, t he experimental results support the expected advantages of wedge struc tures for microwave modulation of the emission current : a low gate vo ltage, a reduced current density, a good thermal behavior.