Core-level shifts in x-ray photoelectron spectroscopy of arsenic defects in silicon crystal: A first-principles study

Jun Yamauchi,Yoshihide Yoshimoto,Yuji Suwa

doi:10.1063/5.0025316

Abstract

We systematically investigated the arsenic (As) 3d core-level x-ray photoelectron spectroscopy (XPS) binding energy and formation energy for As defects in silicon by first-principles calculation with a high accuracy of 0.1 eV by careful evaluation of the supercell size. For As, we adopt a pseudopotential with 3d states as the valence and the spherical hole approximation to ensure the convergence of self-consistent calculation for the XPS binding energy with large size systems. Some of the examined model defects have threefold coordinated As atoms. The XPS binding energies of these As atoms are distributed in the narrow region from −0.66 eV to −0.73 eV in neutral charge states. Such defects in negative charge states have a lower XPS binding energy by about 0.1 eV. From the XPS binding energy and electrical activity, negatively charged defects of a vacancy and two adjacent substitutional As atoms (As2V) are the most probable candidates for the experimentally observed peak at −0.8 eV called BEM from the reference substitutional As peak. Under the experimental condition, we find that As2V−,2− do not deeply trap electrons and are electrically inactive. We also demonstrate the surface effect that surface states near the bandgap decrease the XPS binding energy, which may generate defects with low binding energies similarly to the experimental peak at −1.2 eV called BEL.

Highlights

Arsenic (As) is the most important n-type dopant element in silicon (Si)-based devices
We examined the possibilities of charged states for the defect models whose highest occupied orbitals or lowest unoccupied orbitals of the neutral states are close to the Fermi level
The exception is AsV+, whose donor state in the lower half of the bandgap was evaluated experimentally and theoretically,10 it usually behaves as an acceptor

Summary

Introduction

Arsenic (As) is the most important n-type dopant element in silicon (Si)-based devices. With the scaling down of device size, shallow junctions with high carrier concentrations are required. Various studies have been carried out on the behavior of As atoms in high-concentration regions.. It is very difficult to obtain atomic-level information on dopant behavior. One of the reasons for the difficulty is the low intensity of measurement signals. This is because the dopant concentration is much lower than the number of host atoms, and the proportion of defects at issue is lower than those of all dopants. To compensate for the weak signals, Tsutsui et al utilized high-intensity x-ray beams generated by large synchrotron radiation facilities for detailed x-ray photoelectron spectroscopy (XPS)

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