Composition Dependence of Equal Thickness Fringes in an Electron Microscope Image of GaAs/Al_xGa_1-x As Multilayer Structure

Abstract

A new method is presented for the composition analysis of GaAs/Al x Ga1-x As multilayer structure using transmission electron microscopy. It is found that the position of equal thickness fringe observed at the edge of a cleaved chip is closely related to the composition. Change in Al composition in GaAs/Al x Ga1-x As superstructure is observed as a shift of the equal thickness fringe. Compositional abruptness at the heterointerface and compositional fluctuation in the thin layer can be estimated in the electron microscope image.

Preparation Techniques for Transmission Electron Microscopy

“…The cleavage technique was first established for GaAs/GaAlAs [53]. The sample wafer is polished to about 200pm thickness and then cleaved into small squares 0.5mm x 1 mm in size.…”

Characterizing III–V heteroepitaxial structures

“…23 The most promising TEM method to measure the composition at a nm resolution seems to be the thickness-fringe method. 24 This technique compares brightfield extinction fringes in a sample containing a 90-degree wedge with results of theoretical calculations. The fringe positions are very sensitive to compositional variation.…”

Preparation of (InGa)As/GaAs materials for TEM by one side non‐rotation ion beam thinning

“…A variety of methods have been developed for the preparation of thin foil specimens from these materials (Brown and Sheng, 1988;Goodhew, 1985a; Newcomb et al, 1985). These have varied from methods involving either ion milling (Abrahams and Buiocchi, 1974;Bravman and Sinclair, 1984) or chemical etching (Chu and Sheng, 1984) to methods employing electron beam lithographic techniques (Dobisz et al, 1984;Wetzel and Danner, 1988) and to methods just involving mechanical cleaving (Hetherington, 1988; Kakibayashi and Nagata, 1985). This paper is concerned with the application of ion milling to obtain uniform cross-sectional specimens from (1nGa)AshGaAs multilayers.…”