Defect formation in (100) GaSb by 60keV Sn+ ion-implantation at 150 to 153K was investigated using cross-sectional transmission electron microscopy, SEM and EDX. An anomalous structure consisting of many cells, which looks like a honeycomb, was formed on the surface implanted with 8.9 x 1018/m2. The diameter and the depth of a cell were about 50nm and 220 to 250nm, respectively. The thickness of the walls partitioning the cells was about 10nm. The upper part of the partitioning wall was amorphous and rich in Ga, while the lower part exhibited crystalline structure. A heavily strained region of 50nm thickness, corresponding to the maximum depth of the projected Sn ions, was observed under the cells. This defect structure was compared with similar defects which were observed in ion-implanted GaSb. The defect formation mechanism was discussed, and an explanation based upon movement of the implantation induced point defects was proposed. It was assumed that hills and hollows were formed in the early stage of implantation. The point defects created on the hills do not contribute to the development of the defect structure, because they annihilate almost completely by the recombination of vacancy and interstitial and by the movement to the near surface sink. However, under the hollows, vacancies which escaped recombination remain, and the interstitial atoms, which were highly mobile at low temperatures, migrate far from there to aggregate under the hills. The hollows become deeper by the movement of the remaining vacancies to the surface, and the hills develop into the walls by the migration of the interstitial atoms from the surrounding hollows.

Formation of Anomalous Defect Structure on GaSb Surface by Low Temperature Sn Ion-Implantation. N.Nitta, M.Taniwaki, T.Suzuki, Y.Hayashi, Y.Satoh, T.Yoshiie: Materials Transactions, 2002, 43[4], 674-80