Fermi-level pinning in ErAs nanoparticles embedded in III-V semiconductors

TL;DR

This study uses first-principles calculations to analyze the electronic structure and Fermi-level pinning of ErAs nanoparticles embedded in III-V semiconductors, revealing how size and material influence their electronic properties.

Contribution

It provides the first detailed theoretical investigation of the electronic properties and Fermi-level pinning behavior of ErAs nanoparticles in various III-V semiconductors.

Findings

Spherical ErAs nanoparticles are energetically most favorable.

Fermi level shifts with nanoparticle size, pinning near mid-gap for small sizes.

Fermi level is pinned on an absolute energy scale considering band alignment.

Abstract

Embedding rare-earth pnictide (RE-V) nanoparticles into III-V semiconductors enables unique optical, electrical, and thermal properties, with applications in THz photoconductive switches, tunnel junctions, and thermoelectric devices. Despite the high structural quality and control over growth, particle size, and density, the underlying electronic structure of these nanocomposite materials has only been hypothesized. Basic questions about the metallic or semiconducting nature of the nanoparticles (that are typically < 3 nm in diameter) have remained unanswered. Using first-principles calculations, we investigated the structural and electronic properties of ErAs nanoparticles in AlAs, GaAs, InAs, and their alloys. Formation energies of the ErAs nanoparticles with different shapes and sizes (i.e., from cubic to spherical, with 1.14 nm, 1.71 nm, and 2.28 nm diameters) show that spherical nanoparticles are the most energetically favorable. As the diameter increases, the Fermi level is lowered from near the conduction band to the middle of the gap. For the lowest energy nanoparticles, the Fermi level is pinned near the mid-gap, at about 0.8 eV above the valence band in GaAs and about 1.2 eV in AlAs, and it is resonant in the conduction band in InAs. Our results show that the Fermi level is pinned on an absolute energy scale once the band alignment at AlAs/GaAs/InAs interfaces is considered, offering insights into the rational design of these nanocomposite materials.