Characterization of electron emitting surfaces of diamond and III-V nitrides

Contributors:   Robert J. Nemanich, P.K. Baumann, M.C. Benjamin, S.L. English, J.D. Hartman, A.T. Sowers, and B.L. Ward

ABSTRACT

Wide band gap semiconductors such as diamond and the diamond-related materials of GaN and AlN, exhibit small or even negative electron affinities. Recent results have shown that surface treatments will modify the electron affinity of diamond, causing it to have a negative electron affinity (NEA). For the III-V nitrides of GaN and AlN, results indicate a NEA for some surfaces of AlN and an electron affinity of 3.3 eV for GaN. Alloys of AlGaN exhibit a composition-dependent electron affinity that tends to a value of zero at ∼ 70% AlN. In this study we describe approaches for the characterization of these surfaces using UV photoemission spectroscopy (UPS), position-dependent field emission and photo-electron emission microscopy (PEEM). Measurements are presented of field emission from single crystal p-type (boron doped) diamond with various surface processes. The field emission results are correlated with the surface processes used to establish a NEA surface. The field emission threshold of nitrogen-doped samples is significantly higher than that of p-type diamond; in fact, most surfaces are severely damaged during the emission measurement. The PEEM technique, which combines aspects of UPS and field emission, images the emitted electrons allowing us to establish a true relationship between the emission and the surface morphology. PEEM results for both diamond and nitride surfaces are presented.

Publisher: New Diamond and Frontier Carbon Technology,   Volume: 8,   211-223 ||  Published: 1998-01 ||   Read more...