Analytical model for the optical functions of indium gallium nitride with application to thin film solar photovoltaic cells

This paper presents the preliminary results of optical characterization using spectroscopic ellipsometry of wurtzite indium gallium nitride (InxGa1−xN) thin films with medium indium content (0.38 < x < 0.68) that were deposited on silicon dioxide using plasma-enhanced evaporation. A Kramers–Kronig consistent parametric analytical model using Gaussian oscillators to describe the absorption spectra has been developed to extract the real and imaginary components of the dielectric function (ɛ1, ɛ2) of InxGa1−xN films. Scanning electron microscope (SEM) images are presented to examine film microstructure and verify film thicknesses determined from ellipsometry modeling. This fitting procedure, model, and parameters can be employed in the future to extract physical parameters from ellipsometric data from other InxGa1−xN films.

Graphical abstractReal and imaginary parts of the dielectric function for InxGa1−xN thin film on a silicon dioxide substrate with x = 0.375.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The dielectric function of wurtzite indium gallium nitride has been fit. ► A database of the parameters in the analytical expression are made. ► Optical functions of InxGa1−xN with (0.375 < x < 0.679) films were developed. ► This is the foundation for performance simulations of In-rich InxGa1−xN alloys. ► This is useful for optimization of multi-junction solar photovoltaic devices.