The formation of microsplits and damage rafts in proton-bombarded GaAs

The technique of cross-sectional transmission electron microscopy has been used to study the nature and formation of damage rafts, which act as dislocation sources, in proton-bombarded (5 x 1015, 1016 and 1017 H+ cm-2) and annealed GaAs. The results show that the rafts consist of a planar array of voids lying on the {110} cleavage planes of GaAs. The dislocations generated at these rafts are glissile, of the (a/2) <110> type, and glide on the {111} planes intersecting the rafts. Models are presented to show that these damage rafts originated at microsplits on the {110} cleavage planes of GaAs following the cracking open of small hydrogen-filled platelets on {110} planes when the internal gas pressure exceeds that which is necessary for crack propagation. From the analysis of the results an average diffusion length of ∼ 1 μm was estimated for vacancies in proton-bombarded GaAs at ∼ 9000C. (author)