The crystallinity of deposited films was studied using a PANalytical EMPYREAN MRD XRD with a Cu-anode x-ray tube and 5-axis (x-y-z-v-u) sample stage both in -2 and grazing incidence (GIXRD) configuration. Strain in the films was estimated from the GIXRD measurement for each diffraction peak values of sin 2  and  using the software X'Pert Stress. PANalytical X'Pert PRO with a Cu-anode tube and Bragg-Brentano HD optics was used for -2 measurement and in X-ray Reflectivity (XRR) mode to measure the film thickness. The software PANalytical X'Pert reflectivity was used to fit the XRR data using a two-layer model of the GaN substrate. A LEO 1550 Scanning electron microscope (SEM) with an acceleration energy of 10-20 kV was used to characterise the morphology of the film. The film composition and chemical bonding environments of the atoms in the film were characterized with a Kratos AXIS Ultra DLD X-ray photoelectron spectroscopy (XPS) equipped with Ar (0.5 keV) sputtering source. CasaXPS software was used to evaluate the data. Gaussian-Laurentius functions and Shirley background were used to fit the experimental XPS data. The absorption spectroscopy measurements were conducted using a custom fibre optical setup consisting of a light source (Ocean Optics DH-2000-BAL), a detector (Avantes AvaSpec-Dual) and a bifurcated optical fibre (Ocean Optics BIFBORO-2-1000). An absorption spectrum for the GaN film was collected using a custom software based on LabView (National Instruments) with a Si (100) substrate used as a reference.