Exploring Electronic Confinement in Si:P δ-layers

Abstract

In this thesis, the electronic states of a quantum well system in silicon is investigated. The confinement is induced by a thin dopant profile called a delta-layer, creating an effective two-dimensional metallic region inside a semiconducting bulk environment. The understanding of these systems is of great importance for silicon-based quantum computing applications, which rely on exact knowledge of the dynamics of the quantum well states. The presented results serve to complement existing work in this field, which has mainly been focused towards the extreme case of a single atomic layer dopant profile. Five silicon-phosphorus delta-layer samples with different dopant profile thickness were fabricated by gas dosing and epitaxial growth. The electronic band structure was investigated using angle-resolved photoemission spectroscopy (ARPES) and synchrotron radiation. The energy separations of the three lowest electronic energy bands, known as the 1Gamma, 2Gamma, and 1Delta, were tracked as the delta-layer thickness was changed. Most notably, novel measurements of the 1Delta state in a monolayer is presented, allowing sought-after comparison to existing work. The results suggest taking an alternate view of the band structure in these devices, specifically by reinterpreting the identification of the Gamma states in observations. This new picture speaks in favor of adopting a larger material dielectric constant than previously assumed for these structures, which can reduce current inconsistencies between experimental observations and calculations.