Analysis of strain in ultra-thin GaAs/In 0.2Ga 0.8As/GaAs single quantum well structures by channeling technique

Abstract

The strain in single In 0.2Ga 0.8As layers buried in GaAs is studied by means of ion channeling about off-normal crystallographic axes in major planes: 〈110〉 in (100), 〈112〉 in (110), and planar (110). The results presented here show that beam steering in the channels of the top GaAs overlayer has to be taken into account in spite of the fact that its thickness is much lower than a half of the characteristic pseudo-wavelength of the oscillatory movement of 2 MeV He ions in channels. Monte Carlo simulations of the channeling angular scans have been performed. The perpendicular lattice constant in the tetragonally distorted strained InGaAs layer was found to be 5.81 Å, in excellent agreement with the value predicted by the elasticity theory. The simulated In angular scan profiles appeared to be highly sensitive to the thickness of the GaAs capping layer. It is suggested that the most favourable geometry for evaluating the perpendicular strain, ε ∥, in highly strained thin buried layers is a scan across the 〈110〉 channel in the (100) plane.