Influence of strain, specimen orientation and background estimation on composition evaluation of InAs/GaAs by TEM

Abstract The influence of strain, specimen orientation and background estimation on the accuracy of CELFA results is investigated using displacement vectors, calculated by finite differences, in the Darwin–Howie–Whelan equations. The calculations allow a simulation of the complex amplitudes of the beams, computation of the image Fourier components and application of the CELFA method to the simulated image Fourier components. The evaluated indium concentration can also be compared with the concentration profile used as input for simulation of the displacements. An equation for the true background has been derived and it is shown that background estimation by a polynomial fitting is the major error in the application of the CELFA method. It is also shown that under proper conditions (thickness <70 nm and an orientation such that the centre of the Laue circle is between [20; 0; 0] and [20; 1.75; 0]), the systematic errors, due the presence of strain effects, are not more than about 100 · (ΔX/X true) ≈ ± 5%.