The Photoionization Processes of Deep Trap Levels in n-GaN Films Grown by MOVPE Technique on Ammono-GaN Substrates

In this paper, we present various theoretical models that accurately approximate the spectral density of the optical capture cross-section (sigma e0) obtained through the analysis of photo-capacitance transients using the deep-level optical spectroscopy (DLOS) technique applied to semi-transparent Ni/Au Schottky barrier diodes (SBDs) fabricated on n-GaN films. The theoretical models examined in this study involved a variety of approaches, from the Lucovsky model that assumes no lattice relaxation to more sophisticated models such as the Chantre-Bois and the P & auml;ssler models, which consider the electron-phonon coupling phenomenon. By applying theoretical models to the experimentally determined data, we were able to estimate the photoionization (E0), trap level position (ET), and Franck-Condon (dFC) energy, respectively. In addition, the results of our analysis confirm that the photoionization processes of deep traps in n-GaN grown by the metal-organic vapor-phase epitaxy technique (MOVPE) are strongly coupled to the lattice. Moreover, it was shown that the P & auml;ssler model is preferred for the accurate determination of the individual trap parameters of defects present in n-GaN films grown on an Ammono-GaN substrate. Finally, a new trap level, Ec-1.99 eV with dFC = 0.15, that has not been previously reported in n-GaN films grown by MOVPE was found.