Quantitative Analysis of Al_(1-x)Ga_xAs heterostructures using EELS

摘要

The optimization of the acquisition and the evaluation conditions for the EELS spectra of Al_xGa_(1-x)As heterostructures permits one to find the absolute concentration x with a precision of +-0.02 and to detect changes in concentrations of +-0.01-0.02 for x=0-0.5. The central elment of this optimization is a Bloch wave calculation of electron channeling patterns in order to find a specimen orientatin where electron channeling is minimized without introducing an unacceptable loss of spatial resolution due to sample tilt. Vertical quantum wells in MOCVD grown structures could be quantified and their detailed structure could be found.