Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 98: Nitrides: Bulk material, films, surfaces and quantum wells

HL 98.2: Talk

Friday, March 20, 2015, 09:45–10:00, EW 201

Interaction of GaN(0001) surfaces with potassium and water — •Marcel Himmerlich, Vladimir Irkha, Anja Eisenhardt, Stephanie Reiss, and Stefan Krischok — Institut für Physik and Institut für Mikro- und Nanotechnologien, TU Ilmenau, Germany

Due to its high physical and chemical stability, gallium nitride (GaN) is a promising material for the use in chemical or biological sensor devices. For device optimization and clarification of degradation mechanisms, a profound understanding of the interaction between the GaN surface and the species of the surrounding environment that are aimed to be analysed is essential. Here we present a study on the interaction of GaN(0001) surfaces with potassium and water, motivated by K ions in aqueous environment being important for biosensor applications due to its involvement in fundamental cell metabolism processes. Changes in the chemical and surface electronic properties during the adsorption and coadsorption of K and water on the epitaxial grown GaN surfaces were in-situ characterized by X-ray and ultraviolet photoelectron spectroscopy. The measurements show the formation of K and oxygen related electron states as well as significant changes in the sample work function Φ and surface band bending V_bb. Water adsorption leads to a slight increase in Φ, while K adsorption and coadsorption of K and water induce a pronounced work function decrease. Furthermore, K increases the surface upward band bending of GaN(0001), while during the interplay of K with water a reduction in V_bb is observed. The interplay between surface and adsorbate electron states and the occurring chemical and charge transfer processes will be discussed.