Semiconductor cold electron emission device

Claim 1

A cold emission semiconductor device comprising a first layer of GaAlP, and of several hundred Angstroms thickness and of n-type conductivity; a second layer of GaAlP of p-type conductivity and of a thickness less than the diffusion length of electrons, and whose effective forbidden band gap is smaller than that of said first layer, said first and said second layers being intimately in contact with each other through epitaxial growth and with substantial lattice match to form a heterojunction, said second layer having a surface opposite said heterojunction with zero or negative electron affinity for emission of electrons, a first electrode connectable to said first layer, and a second electrode connectable to said second layer with the distance between said second electrode and said heterojunction being more than the diffusion length of electrons, and means for applying a potential to said electrodes to bias said heterojunction and cause said first layer to generate electrons which are subsequently injected into said second layer and without substantially any recombination emitted from said surface of said second layer, wherein said second layer has a graded forbidden band gap.