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× and is attributed to a (+/0) transition of antisite defects. The weak 0.5-eV peak is tentatively attributed to a (++/+) transition of the antisite defects. The 0.15- and 1.1-eV peaks that have densities of 1.3× and 0.8× , respectively, are attributed to 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 antisite defects. From the density of the interface states near the Fermi level, i.e., ∼1× , it is shown that dφ/d (φ: barrier height in GaAs, : metal electronegativity) is 0.24, indicating that the Fermi level is pinned partly by the antisite defects and that fixed oxide positive charges with a density of (2–3)× are present at the GaAs/oxide interface.
- Received 23 March 1995
DOI:https://doi.org/10.1103/PhysRevB.52.5781
©1995 American Physical Society