An examination of tellurium ion-implanted GaAs by transmission electron microscopy

Abstract

The effect of implanting high energy tellurium ions into single crystal GaAs has been investigated by transmission electron microscopy. Results from annealing experiments on specimens implanted at room temperature show that two anneal stages centred near 200 and 600° C occur, the actual anneal temperature being dose dependent. Non-crystalline surface layers were formed after implanting doses in the range 5×1013 to 5×1015 ions cm−2 at room temperature. However, implanting similar doses at 180° C caused no change in crystallinity. Thus the low temperature anneal stage which is the epitaxial recrystallization of the non-crystalline material, does not occur for the higher implant temperature. The high temperature anneal stage is associated with the annealing out of tiny defects such as twins and/or stacking faults leaving a single crystal containing only dislocation loops. The anneal stages observed by electron microscopy correlate with changes in sheet resistivity and Rutherford backscattering measurements on similar material. It is suggested that changes in dislocation loop size and density at high temperatures are coincident with the attainment of electrical activity.