Observation and origin of the $\Delta$-manifold in Si:P $\delta$-layers

TL;DR

This study reveals the existence of the $\Delta$-manifold quantum well states in Si:P $\delta$-layers and demonstrates how their carrier properties can be tuned by adjusting the dopant layer thickness.

Contribution

It provides the first experimental observation of the $\Delta$-manifold in Si:P $\delta$-layers and shows how quantum confinement influences carrier characteristics.

Findings

Observation of the $\Delta$-manifold states using photoemission spectroscopy.

Carrier population within the $\Delta$-manifold is tunable by dopant layer thickness.

Quantum confinement effects are confirmed in ultra-thin dopant layers.

Abstract

By creating a sharp and dense dopant profile of phosphorus atoms buried within a silicon host, a two-dimensional electron gas is formed within the dopant region. Quantum confinement effects induced by reducing the thickness of the dopant layer, from $4.0$\,nm to the single-layer limit, are explored using angle-resolved photoemission spectroscopy. The location of theoretically predicted, but experimentally hitherto unobserved, quantum well states known as the $\Delta$-manifold is revealed. Moreover, the number of carriers hosted within the $\Delta$-manifold is shown to be strongly affected by the confinement potential, opening the possibility to select carrier characteristics by tuning the dopant-layer thickness.