ELECTRON-EMISSION PROPERTIES OF CRYSTALLINE DIAMOND AND III-NITRIDE SURFACES

Wide bandgap semiconductors have the possibility of exhibiting a negat ive electron affinity (NEA) meaning that electrons in the conduction b and are not bound by the surface. The surface conditions are shown to be of critical importance in obtaining a negative electron affinity. U V-photoelectron spectroscopy can be used to distinguish and explore th e effect. Surface terminations of molecular adsorbates and metals are shown to induce an NEA on diamond. Furthermore, a NEA has been establi shed for epitaxial AlN and AlGaN on 6H-SiC. Field emission measurement s from flat surfaces of p-type diamond and AlN are similar, but it is shown that the mechanisms may be quite different. The measurements sup port the recent suggestions that field emission from p-type diamond or iginates from the valence band while for AlN on SiC, the field emissio n results indicate emission from the AlN conduction band. We also repo rt PEEM (photo-electron emission microscopy) and FEEM (field electron emission microscopy) images of an array of nitride emitters. (C) 1998 Elsevier Science B.V. All rights reserved.