Formation of a p-n junction on the GaAs-surface by an Ar+ ion beam
  The core-level and valence band electronic structure of the well-defined near-surface layer of n-GaAs (100) has been studied by synchrotron-based high-resolution photoelectron spectroscopy before and after modification of the layer by an Ar+ ion beam in the 1.5 - 2.5 keV energy range. Conversion of the conductivity type from n into p has been revealed in the irradiated layer several nm thick. The effect manifests itself in shifts of the core-levels and valence band edge by the value comparable to the bandgap width. Transformation on the conductivity type has been assumed to be caused by Ga-antisite point defects generated by ion bombardment. The possibility of local formation of a p-n nanojunction within the ion-beam spot has been shown. 
V.M. Mikoushkin, V.V. Bryzgalov, S.Yu. Nikonov, A.P. Solonitsyna, D.E.   Marchenko
cond-mat.mtrl-sci