We have found that the extremely extended platelets of about 1 &mgr;m in diameter are formed in GaAs by He-ion implantation and subsequent annealing at 250 and 300 °C for the short period of 180–300 s. We have shown that the platelets are extended not on the most easily cleavaged {110}-type planes but on {111}-type planes. The platelets give rise to the extra transmission electron diffraction spots. The analysis of the diffraction, combined with electron microscopy data, has shown that unreconstructed interior {111} surfaces, oppositely bent, are created in GaAs. ©1997 American Institute of Physics.