The natures of defect centers, which were introduced by 30keV Ga+ focussed ion-beam bombardment of (100) surfaces, were studied in situ by means of scanning tunnelling spectroscopy. The defect centers were identified as being electron traps which lay below the surface state conduction band; each with an active area of about 20nm2. An areal ion-dose of 1013/cm2 was sufficiently low that no significant surface sputtering was observed by topographic imaging. This suggested that the features which were observed by scanning tunnelling spectroscopy were not related to gross damage.

Electrically active defect centers introduced by Ga+ focussed ion beam irradiation of GaAs(100) S.J.Brown, P.D.Rose, G.A.C.Jones, E.H.Linfield, D.A.Ritchie: Applied Physics Letters, 1999, 74[4], 576-8