Combined study of multiple-quantum-well structures using high resolution electron microscopy imaging and analysis in conjunction with the position-sensitive atom probe

Abstract

InGaAs/InP multiple-quantum-wells have been the subject of a joint study using three, individually powerful, techniques that give information on the chemistry, morphology, and crystallography of materials at near atomic dimensions. A high resolution scanning transmission electron microscope with a field emission source has been used to obtain chemical and crystallographic data. Energy dispersive x-ray spectroscopy and electron energy loss spectroscopy have been used, with nanometer resolution, to map the chemical composition across the wells and barrier layers. High resolution electron microscopy has been carried out on the same specimens to analyze the structure of the quantum-well/barrier layer interfaces at the atomic level. The experimental images have been compared with simulated images calculated with use of the multislice technique, to ensure correct interpretation of the images. The third technique used, position-sensitive atom probe, has been applied to the study of these same materials, although specimens are unfortunately not directly compatible with the above two techniques. The chemistry of the wells can be obtained quantitatively with use of both the position-sensitive and normal atom probe configurations, and the results are directly comparable with those obtained by the scanning transmission electron microscope.