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Mapping of AlxGa1–xAs band edges by ballistic electron emission spectroscopy

Cheng, X.-C. and Collins, D. A. and McGill, T. C. (1997) Mapping of AlxGa1–xAs band edges by ballistic electron emission spectroscopy. Journal of Vacuum Science and Technology A, 15 (4). pp. 2063-2068. ISSN 0734-2101. doi:10.1116/1.580609.

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We have employed ballistic electron emission microscopy (BEEM) to study the energy positions in the conduction band of AlxGa1 – xAs. Epilayers of undoped AlxGa1 – xAs were grown by molecular beam epitaxy on conductive GaAs substrates. The Al composition x took on values of 0, 0.11, 0.19, 0.25, 0.50, 0.80 and 1 so that the material was examined in both the direct and indirect band gap regime. The AlxGa1 – xAs layer thickness was varied from 100 to 500 Å to ensure probing of bulk energy levels. Different capping layers and surface treatments were explored to prevent surface oxidation and examine Fermi level pinning at the cap layer/AlxGa1 – xAs interface. All samples were metallized ex situ with a 100 Å Au layer so that the final BEEM structure is of the form Au/capping layer/AlxGa1 – xAs/bulk GaAs. Notably we have measured the Schottky barrier height for Au on AlxGa1 – xAs. We have also probed the higher lying band edges such as the X point at low Al concentrations and the L point at high Al concentrations. Variations of these critical energy positions with Al composition x were mapped out in detail and compared with findings from other studies. Local variations of these energy positions were also examined and found to be on the order of 30–50 meV. The results of this study suggest that BEEM can provide accurate positions for multiple energy levels in a single semiconductor structure.

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Additional Information:© 1997 American Vacuum Society. (Received 11 October 1996; accepted 17 January 1997) This study was supported in part by the Office of Naval Research under Grant No. N00019-89-J-00014 and Air Force Office of Scientific Research under Grant No. F49620-93-J-0258. In addition, the authors would like to thank Rob Miles for his part in constructing the BEEM apparatus.
Funding AgencyGrant Number
Office of Naval Research (ONR)N00019-89-J-00014
Air Force Office of Scientific Research (AFOSR)F49620-93-J-0258
Subject Keywords:aluminium compounds; gallium arsenide; III-V semiconductors; field emission electron microscopy; semiconductor epitaxial layers; conduction bands; stoichiometry; energy gap; surface treatment; Fermi level; Schottky barriers
Issue or Number:4
Record Number:CaltechAUTHORS:CHEjvsta97
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3231
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Deposited On:23 May 2006
Last Modified:08 Nov 2021 19:54

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