STRAIN AND CRITICAL THICKNESS IN GaSb/AlSb: AN ION CHANNELING STUDY.

Strain and the critical thickness of the onset of strain relief in thin films of AlSb on GaSb(100) have been determined by a combination of ion channeling techniques and particle induced x-ray emission (PIXE). The maximum strain in the films agrees very well that calculated from bulk elasticity data. The critical thickness as measured by the ion channeling experiment is ~140+- 25angstroms. Films exceeding the critical thickness do not relieve the strain immediately but rather show a gradual relaxation up to ~1000angstroms. The results are compared with theoretical models of strain relief and critical thickness. Issues related to the protection of the AlSb films from oxidation, beam damage, and the use of PIXE have been addressed. A protective cap of ~200angstroms of Be was found to give the best performance.