Berlin 2018 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 34: Carbon: Diamond, nanotubes, Buckyballs
HL 34.1: Vortrag
Donnerstag, 15. März 2018, 09:30–09:45, EW 015
Tunable carrier density of two-dimensional hole gases on diamond — •Dennis Oing, Martin Geller, Nicolas Wöhrl, and Axel Lorke — University of Duisburg-Essen, 47057 Duisburg, Germany
Since diamond has a large band gap of 5.45 eV, it shows a vanishing intrinsic charge carrier density at room temperature.
However, surface conductivity, induced by a two-dimensional hole gas on the surface, can be established by hydrogen termination and accumulation of an adsorbate layer.
Here, we investigate two-dimensional hole gases (2DHGs) on chemical-vapor-deposition-(CVD)-grown diamond after hydrogen plasma treatment and exposure to ambient atmosphere. The 2DHGs are characterized using temperature-dependent Hall experiments.
The influence of the surface functionalization, determined by X-ray photoelectron spectroscopy (XPS), on the carrier density and mobility is evaluated.
Hall measurements reveal that the carrier density is increasing from 7.6· 1011 cm−2 to 1.5· 1013 cm−2 with increasing amounts of oxygen adsorbed at the surface. In this range, the carrier density remains constant over a temperature range between 4.2 K and 325 K. For oxygen concentrations above 2.2 % (relative XPS signal), the charge carrier density decreases again and becomes temperature dependent.
This supports a model based on oxygen-related centers that lead to the transfer of electrons from the surface to the adsorbate layer.