An x-ray photoelectron spectroscopy study of Fermi level position and surface composition during formation and removal of oxides on InP

An x-ray photoelectron spectrometer coupled with an ultrahigh vacuum specimen preparation chamber was used to study the formation and removal of surface oxides on n- and p-type InP surfaces. Multiple oxide phases were formed by surface oxidation with molecular oxygen or UV/ozone. On n-type InP, the surface Fermi level initially moved down to 0.3 eV below the conduction band minimum (CBM) with low oxygen exposures but finally pinned at 0.1 eV with exposures higher than 1012 L. On p-type InP, the Fermi level moved monotonically towards the CBM and eventually pinned at 0.6 eV for an oxygen exposure higher than 1012 L. Although more indium and phosphorus oxides were formed upon prolonged air or ozone exposure, these final pinning positions were the same as for pure dry oxygen. The surface oxides could be desorbed at 458 °C resulting in a reduced surface band bending of <0.3 eV on both n- and p-type samples.