TEM and HAADF STEM Imaging of Dislocation Loops in Irradiated GaAs
J.H. Neethlinga, A. Janse Van Vuurena, E.J. Oliviera, P.A. Van Akenb
aCentre for HRTEM, Nelson Mandela University, Port Elizabeth, South Africa
bStuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Stuttgart, Germany
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This paper compares earlier transmission electron microscopy results of dislocation loops generated in n-type GaAs by 1 MeV electron and fast neutron irradiation with recent Cs-corrected high angle annular dark field scanning transmission electron microscopy imaging of {110} and {111} dislocation loops in neutron irradiated and annealed (600° for 20 min) n-type GaAs. High angle annular dark field scanning transmission electron microscopy revealed that the {110} loop plane consists of two layers of Ga and As atoms, which is consistent with the model for a {110} pure-edge interstitial dislocation loop in GaAs. The loop plane of the {111} interstitial loop consists of one layer of Ga and As atoms while the stacking sequence across the loop is consistent with that of an extrinsic stacking fault. The projected positions of the Ga and As atom columns across the extrinsic stacking fault plane of the {111} loop indicate polarity continuation across the loop and the preservation of charge neutrality. The annealing stage at 500° found to be the minimum temperature for small dislocation loop formation visible in transmission electron microscopy, agrees with the final annealing stage of 400-600° for the electrical conductivity of electron irradiated n-type GaAs. It is proposed that {110} loops in proton bombarded GaAs are the same type of interstitial loops found in neutron irradiated GaAs while hydrogen platelets form on {111} planes in GaAs exposed to a hydrogen plasma at 180° or in high-dose proton bombarded GaAs.

DOI:10.12693/APhysPolA.136.245
PACS numbers: 61.72.Ff, 61.72.Nn, 61.72.uj