AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP4
Bevel Crater SIMS for Auger Analysis of Laterally Oxidized AlGaAs/GaAs Multilayers

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: S.A. Wight, National Institute of Standards and Technology
Authors: S.A. Wight, National Institute of Standards and Technology
G. Gillen, National Institute of Standards and Technology
P. Chi, National Institute of Standards and Technology
A. Fahey, National Institute of Standards and Technology
A. Roshko, National Institute of Standards and Technology
K. Bertness, National Institute of Standards and Technology
Correspondent: Click to Email
Recently, in support of a project to engineer strain in compound photonic semiconductors, we employed a combination of Secondary Ion Mass Spectrometry (SIMS), Auger Electron Spectroscopy (AES), and Scanning Electron Microscopy (SEM) to characterize MBE grown, laterally wet-thermal oxidized, Al@sub.98@Ga@sub.02@As layers in an attempt to determine compositional uniformity through the oxide layers. Typical samples for this study consist of alternating layers of Al@sub x@Ga@sub 1-x@As (where x is between 0.90 and 1.0) and GaAs. Each AlGaAs layer is 80.0 nm thick and is separated from adjacent layers by 150 nm of GaAs. The surface is capped with 200 nm of GaAs. Each sample has a series of trenches (spaced 100 µm apart) etched through the multilayer to expose the buried AlGaAs layers. The lateral extent of oxidation was designed to be 25 µm from the trench edge. An external raster waveform was used in place of the standard digital raster to produce bevel craters on a commercial SIMS instrument. Beveled samples were analyzed using O2+ and Cs+ microbeam imaging in the SIMS and by AES/SEM in a commercial scanning Auger instrument. Bevels were cut in AlGaAs samples using Cs, O and Ga + primary ion beams at several different energies. Both Cs+ and Ga+ beveling produced very distorted bevels resulting from the large sputter rate differences between oxidized and unoxidized regions and a high degree of surface topography as determined by SEM imaging. Best results were obtained by using O2+ bombardment for bevel production. Currently, we are using Ar+ sputtering at a few keV impact in the Auger instrument to remove the primary beam oxygen before analysis.