Electrically active defect centers induced by Ga+ focused ion beam irradiation of GaAs(100)

The electronic nature of defect centers induced by 30 keV Ga+ focused ion b eam irradiation of GaAs(100) has been studied in situ by scanning tunneling spectroscopy (STS). The defect centers were identified as electron traps l ying below the surface state conduction band, each with an active area of a pproximately 20 nm(2). An areal ion beam dose of 1 x 10(13) cm(-2) was suff iciently low that no significant surface sputtering was observed by topogra phic imaging which suggests that the features. observed by STS are not rela ted to gross physical damage. Spatial STS measurements also allow a lateral profile of a focused ion beam patterned line to be determined accurately, thereby setting a resolution limit on the direct write technique for nanosc ale lithography. (C) 1999 American Institute of Physics. [S0003-6951(99)049 04-9].