The Effects and Application of Phosphonic Passivation on Gallium Nitride Using a Continuous Series of Modifiers ; Die Auswirkungen und Anwendung der Phosphonpassivierung auf Galliumnitrid unter Verwendung einer kontinuierlichen Reihe von Modifikatoren

In this thesis, a route towards a flexible hybrid organic- inorganic LED based on a Förster resonant energy transfer from gallium nitride to an organic emitter is shown. To this end, the electronic and chemical properties of gallium nitride (1100) and (0001) surfaces with different surface modifications, using a consecutive series of phosphonic organic selfassembled monolayers (SAMs), are determined and compared to clean etched surfaces. The surface electronic properties are quantified using X-ray photoelectron spectroscopy, Kelvin probe, UV-Vis spectroscopy, and IV curves, while goniometry gives insight into the wettability of the sample and, thus, a measure of quality control for the SAM passivation. Not only does the surface passivation allow to vary the work function by several hundred meV, but it modifies the band bending of both gallium nitride orientations between -0.4 to 0.6 eV. Furthermore, the band bending was reduced to less than 0.12 eV. This work shows devices smaller than 90 nm in diameter; further improvements on the band bending should enable GaN devices smaller than 20 nm. One such route will be shown by employing hybrid SAMs made up of two different SAM precursor molecules. Here, the SAM properties' linear relationship on the precursor molecules' blend will be shown.The application of the surface modification on the work function was shown for a simple p-n gallium nitride PEDOT hybrid diode, which exhibits a tunable turn-on voltage and improved ideality factor. The tuning comes from the change in the surface dipole of the different SAMs; at the same time, the independence of the surface photo-voltage from both the surface hydroxyl groups and band bending is shown. The PEDOT was deposited in a novel oMLD setup that is not part of this work but was characterized as part of it. All of the results shown were brought together in the final proof of concept electrically driven hybrid LED. The LED shows bright luminescence only for a correctly matched organic emitter with the correct surface ...