Indium content measurements in metamorphic high electron mobility transistor structures by combination of x-ray reciprocal space mapping and transmission electron microscopy

Abstract

We propose a method to determine the indium concentrations x and y in the InyAl1−yAs/InxGa1−xAs metamorphic structures. This approach is based on the combination of two experimental techniques: (i) reciprocal space mapping (RSM) to determine the average In composition in the InAlAs layers and (ii) transmission electron microscopy (TEM) using the intensity measurements of the chemically sensitive (002) reflection from dark-field images to determine the composition in the InGaAs quantum well. We apply this method to a InyAl1−yAs/InxGa1−xAs metamorphic high electron mobility transistor, with x and y approximately equal to 0.35. Furthermore, we present an original and straightforward way to evaluate experimental errors in the determination of composition and strain with the RSM procedure. The influence of these errors on the TEM results is discussed. For In concentrations in the 30%–40% range, the accuracy of this simple method is about 0.5% on the In composition in the InGaAs quantum well.