Direct measurement of 2DEG states in shallow Si:Sb $\delta$-layers

TL;DR

This study directly measures the electronic structure of high-density Sb dopant layers in silicon, demonstrating their similarity to Si:P systems and highlighting Sb's potential as a practical alternative for quantum device applications.

Contribution

It provides the first direct observation of the conduction band states in Si:Sb δ-layers, confirming their confinement and electronic similarity to Si:P systems.

Findings

Conduction band states are occupied and observable via photoemission.

The Γ state extends about 1 nm out-of-plane, slightly wider than dopant distribution.

Sb δ-layers are feasible for quantum devices, with advantages over P.

Abstract

We investigate the electronic structure of high-density layers of Sb dopants in a silicon host, so-called Si:Sb $\delta$-layers. We show that, in spite of the known challenges in producing highly confined Sb $\delta$-layers, sufficient confinement is created such that the lowest conduction band states ($\Gamma$ states, studied in depth in other silicon $\delta$-layers), become occupied and can be observed using angle-resolved photoemission spectroscopy. The electronic structure of the Si:Sb $\delta$-layers closely resembles that of Si:P systems, where the observed conduction band is near-parabolic and slightly anisotropic in the $\mathbf{k}_\parallel$ plane. The observed $\Gamma$ state extends ~ 1 nm in the out-of-plane direction, which is slightly wider than the 1/3 monolayer thick dopant distribution. This is caused by a small segregation of the dopant layer, which is nevertheless minimal when comparing with earlier published attempts. Our results serve to demonstrate that Sb is still a feasible dopant alternative for use in the semiconductor $\delta$-layer platform, providing similar electronic functionality to Si:P systems. Additionally, it has the advantages of being less expensive, more controllable, safer to handle, and more compatible with industrial patterning techniques. Si:Sb is therefore a viable platform for emerging quantum device applications.