Negative electron affinity and electron emission at cesiated GaN and AlN surfaces

The electronic structure of GaN and AlN 0001.surfaces and modification by cesium Cs.adsorption are investigated via ultra-violet and X-ray photoemission spectroscopy UPS, XPS.and total yield spectroscopy. The electron affinity EA. of the clean and ordered 1=1 surfaces is found to be equal to 3.3 and 1.9 eV for GaN and AlN, respectively. Cs adsorption with the help of oxygen pre-treatment in the case of GaN.reduces EA on both surfaces by about 2.6–2.8 eV, leading to true negative electron affinity NEA.in the case of AlN and effective NEA in the case of GaN. Total yield spectroscopy confirms NEA on both surfaces. q2000 Elsevier Science B.V. All rights reserved