ANALYSIS OF STRAIN IN ULTRA-THIN GAAS IN0.2GA0.8AS/GAAS SINGLE-QUANTUM-WELL STRUCTURES BY CHANNELING TECHNIQUE/

The strain in single In0.2Ga0.8As layers buried in GaAs is studied by means of ion channeling about off-normal crystallographic axes in majo r planes: (110) in (100), (112) in (110), and planar (110). The result s presented here show that beam steering in the channels of the top Ga As overlayer has to be taken into account in spite of the fact that it s thickness is much lower than a half of the characteristic pseudo-wav elength of the oscillatory movement of 2 MeV He ions in channels. Mont e Carlo simulations of the channeling angular scans have been performe d. The perpendicular lattice constant in the tetragonally distorted st rained InGaAs layer was found to be 5.81 Angstrom, in excellent agreem ent with the value predicted by the elasticity theory. The simulated i n angular scan profiles appeared to be highly sensitive to the thickne ss of the GaAs capping layer. It is suggested that the most favourable geometry for evaluating the perpendicular strain, epsilon(perpendicul ar to), in highly strained thin buried layers is a scan across the (11 0) channel in the (100) plane.