CONFERENCE SCOPE:
New trends in nanoelectronics
INSTITUTION:
Pontificia Universidad Católica del Perú, Peru
TITLE:
Revisiting Effective Mass, Burstein Moss Shift and Bandgap Narrowing in Degenerate Al-Doped ZnO Thin Films: Bridging Experiment and Theory
ABSTRACT:
This study presents a comprehensive carrier effective mass analysis of Al-doped ZnO (AZO) nanometric thin films comparing two non-parabolic band dispersion approximations, i.e. with (Nelsson) and without (Piserkiewicz) considering thermal-disorder-induced tail states. Based on the latter, it is possible to retrieve electron effective mass and non-parabolicity parameters consistent with the sample’s optical bandgap. Plasma frequency modeling, considering AZO’s polar nature, corroborated by Hall-effect-derived carrier densities, enables the determination of band-edge parameters across non-degenerate to degenerate regimes. Samples spanning varied charge carrier densities were synthesized via RF sputtering with active substrate cooling and post-annealing to systematically probe optoelectronic behavior. A refined dispersion model accounting for excitonic absorption and Urbach tail states enhances the optical bandgap estimation accuracy. The above obtained parameters, along with the interplay of Burstein-Moss shift and bandgap renormalization effects, are quantitatively resolved, revealing doping-induced spectral shifts in the optical absorption edge.
Derived parameters such as hole effective mass, absorption edge onset, and Mott critical density, along with localization phenomena, provide deeper insight into carrier transport and validate the modeling framework. This analysis highlights consistent bandgap underestimation in models omitting valence band effects, underscoring the need for comprehensive band structure treatment. First-principles calculations across aluminum concentrations support experimental trends, with scaled Fermi energy modeling unifying parabolic and non-parabolic regimes. This integrated approach reconciles prior discrepancies and offers a general framework for tailoring the electronic structure of AZO thin films and other degenerate transparent semiconductors.