Oxygen related defects in high energy ion irradiated GaAs

(1 1 0) surface of n-type GaAs is subjected to 4 MeV oxygen ions at different fluences ranging from 1 x 10(12) to 1 x 10(14) ions-cm(-2). The cold emission from the defect states is measured by surface sensitive technique of thermally stimulated exo-electron emission (TSEE) spectroscopy. This method is used for studying the oxygen related electronically active defects in the surface region (10-40 Angstrom). Virgin GaAs showed two active defect levels at 0.67 and 0.92 eV below the conduction band edge. After irradiation the nature of defects get modified and there appears to be more number of defect levels after oxygen ion irradiation. The level detected at 0.74 eV is attributed to the O-V-As, (oxygen and arsenic vacancy complex). The work function measurements, using the retarding field diode method, indicated that the oxygen related defects move the surface Fermi level to a certain extent and modify the electronic properties. The change in the workfunction is attributed to the movement of Fermi level from its position in the band gap when subjected to different fluences of oxygen ions. (C) 1999 Elsevier Science B.V. All rights reserved.