Remote plasma enhanced chemical vapour deposition growth and characterisation of polycrystalline indium nitride thin films
thesisposted on 28.03.2022, 15:04 by Patrick Po-Tsang Chen
This thesis investigates the growth temperature dependent apparent band-gap shift in polycrystalline indium nitride (InN) thin-films that were grown using the remote-plasmaenhanced chemical vapour deposition (RPECVD) method. -- The polycrystalline InN thin-films were grown between 200 and 570 °C on various types of substrates, including c-plane sapphire, n-type silicon, gallium nitride template, borosilicate glass, Schott glass, and cover glass (microscope glass slide cover slip). Trimethylindium and nitrogen gas were used as the precursors for indium and nitrogen, respectively. Nitrogen gas was also used as the carrier gas for the indium precursor vapour. Reactive nitrogen radicals were produced by a remote nitrogen-plasma discharge, which was induced by a microwave electromagnetic field with a frequency of 2.45 GHz. -- A comprehensive range of sample characterisation analyses was conducted. The sample optical properties were examined by optical transmission measurements. The electronic characteristics were determined by Hall effect measurements. The physical and morphological characteristics were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron-backscattered diffraction (EBSD). Compositional characterisation was carried out using X-ray photoelectron spectroscopy (XPS), low-energy electron-induced X-ray emission spectrometry (LEXES), elastic recoil detection analysis (ERDA), and secondary ion mass spectroscopy (SIMS). Finally, electronic structure characterisation was performed using synchrotron soft X-ray absorption (SXA) and soft X-ray emission (SXE) techniques. -- The research outcomes are presented in six parts and include eleven publication works, which were either published or submitted for publication. -- The growth kinetics of these polycrystalline InN thin-films were found to be sensitive to the growth conditions used, indicating a reaction limited process. This resulted in a regime where the thin-film characteristics had a strong dependency on growth temperature. The measured apparent band-gap was between ~ 0.9 and ~ 2.3 eV. This phenomenon was hypothesised to originate from the combined effects of changes in the In-N bonding characteristics and the presence of an increased free electron density in the material. The InN films with apparent band-gaps < ~ 1.7 eV appeared to have an ionic-like bonding characteristic, while the samples with > ~ 1.8 eV were suggested to have a more covalent-like bonding characteristic. Thus, they should be treated as two different electronic materials.