Dechanneling analysis of disorder in (100) gallium arsenide

Abstract

The methods of transmission electron microscopy and high resolution RBS/channeling with MeV energy He+ ions have been applied to a study of defect structures in ion implanted (100) GaAs. Implant conditions (substrate temperature 102 K, implants of 100 keV Te+ to fluences between 4×1013 and 2×1014 cm-2) and anneal schedule (15 min at 623 K) were chosen to promote the formation of twins in the near-surface region of the epitaxial regrowth layer. TEM diffraction patterns and dark field micrographs from the annealed samples gave evidence for twinning on {111} planes. The residual amorphous layer thickness was estimated to be less than 2 nm for all cases. Rutherford backscattering spectra were recorded for He+ ion channeling in the [001] direction and dechanneling characteristics determined for a range of ion beam energies. From the combined analyses a picture emerges of a regrowth layer rich in twins, initially with the 〈221〉 directions of the twins parallel to the 〈001〉 directions of the original crystal, but becoming progressively misoriented towards the surface. Show more