DIRECT EVIDENCE OF ER ATOMS OCCUPYING AN INTERSTITIAL SITE IN METALORGANIC CHEMICAL VAPOR DEPOSITION-GROWN GAASER

Er doped GaAs grown by metalorganic chemical vapor deposition is studied by the Rutherford backscattering channeling method. We directly confirmed, for the first time, that Er ions occupy a somewhat displaced tetrahedral interstitial site, rather than a substitutional site, in the GaAs host. This is concluded from the observation of a remarkable peak of the doped Er ions caused by the flux peaking effect in the [110] channeling direction. Also leading to this conclusion is the fact that the ratios of the [111] and [100] channeling yields to the random yields for Er ions were larger than those for the GaAs host. Moreover, we observe peak shifts towards the higher energy region in the [110] spectra compared to the random spectra. This is due to the lower stopping power of He ions in the GaAs host in the channeling direction than in the random direction. We deduce the strikingly small stopping power ratio of the [110] to the random incidence is also discussed.