Energy distribution of interface states in the band gap of GaAs determined from x-ray photoelectron spectra under biases

H. Kobayashi, K. Namba, T. Mori, and Y. Nakato
Phys. Rev. B 52, 5781 – Published 15 August 1995
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Abstract

The energy distribution of interface states in the GaAs band gap is determined for metal-oxide-semiconductor devices with an ultrathin thermal oxide layer of ∼3.8 nm, from measurements of x-ray photoelectron spectra under biases. The energy distribution has a peaked structure with four peaks at ∼0.15, ∼0.5, ∼0.75, and ∼1.1 eV above the valence-band maximum (VBM). The 0.75-eV peak has the highest density of ∼1.9×1012 cm2 and is attributed to a (+/0) transition of AsGa antisite defects. The weak 0.5-eV peak is tentatively attributed to a (++/+) transition of the AsGa antisite defects. The 0.15- and 1.1-eV peaks that have densities of 1.3×1012 and 0.8×1012 cm2, respectively, are attributed to GaAs antisite defects and Ga vacancy defects, respectively. The interface Fermi level of GaAs is located at 0.85 eV above the VBM, indicating that it is strongly affected by the AsGa antisite defects. From the density of the interface states near the Fermi level, i.e., ∼1×1013 cm2 eV1, it is shown that dφ/dχM (φ: barrier height in GaAs, χM: metal electronegativity) is 0.24, indicating that the Fermi level is pinned partly by the AsGa antisite defects and that fixed oxide positive charges with a density of (2–3)×1012 cm2 are present at the GaAs/oxide interface.

  • Received 23 March 1995

DOI:https://doi.org/10.1103/PhysRevB.52.5781

©1995 American Physical Society

Authors & Affiliations

H. Kobayashi, K. Namba, T. Mori, and Y. Nakato

  • Department of Chemistry, Faculty of Engineering Science, and Research Center for Photoenergetics of Organic Materials, Osaka University, Toyonaka, Osaka 560, Japan

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Issue

Vol. 52, Iss. 8 — 15 August 1995

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