Studies of electronic and sensing properties of epitaxial InP surfaces for applications in gas sensor devices

Overview & Synopsis

The aim of this Thesis was a realization and a characterization of a novel nitrogen dioxide (NO2) sensor on the base of n-type indium phosphide (InP) epitaxial layers. First, a short survey through the air pollutants as well as their detection and monitoring methods is presented. After, the physical and chemical properties of InP (taken from literature) are detailed. In the experimental part, the description as well as the fabrication method of the gas sensor devices with different n-InP layer thickness (from 0.2 to 0.4 μm) are shown. The results of the tests under NO2 (less than 50 ppb) as well as the results of the tests at different temperatures for different sensor series are also given. The methods and results of chemical characterization, like X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) combined with ion sputtering and Atomic Force Microscopy (AFM) are presented and applied in order to get the in-depth composition profile of InP native oxides; before and after gas action. The obtained results by Van der Pauw method are also presented i.e., the charge carrier concentration before and after action of NO2. Finally, theoretical analysis of the influence of surface states and temperature on the electronic parameters of the InP near-surface region was also performed. Both experimental data and theoretical analysis showed the influence of InP native oxide layer on the sensing mechanism and surface phenomena (surface Fermi level pinning, sensor stability, etc.) of InP. The results of the theoretical and experimental analysis are coherent and allow to develop a model of the gas action on the n-InP epitaxial layers.