Observation and origin of the manifold in Si:P layers

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.