EXFOLIATION OF GAAS CAUSED BY MEV H-1 AND HE-4 ION-IMPLANTATION AT (100)AXIAL, (110)AXIAL AND RANDOM ORIENTATIONS

The exfoliation procedure of the ion range determination of gaseous im plants in single crystal GaAs is investigated. The correlation of the observed crater depth with the ion range is studied for random, [100] and [110] axial orientation high dose implantations of 1.5-2.5 MeV H-1 and He-4 ions. Depending on the experimental conditions, the crater d epths corresponded to range values between the modal range and the ran ge maximum. The observed crater depths could be related to the actual He concentration depth distributions by determining the profiles of th e He-4 implants by 2.7 MeV proton backscattering. The implantation par ameters affecting the exfoliation process, and especially the increase rate of the sample temperature, are investigated. The range distribut ion parameters for the 1.5 MeV He-4 implants are presented.