Many-body, Pauli blocking and carrier-impurity interaction effects on the band gap of aluminum doped zinc oxide thin films: A new method to evaluate both hole and electron effective masses of degenerate semiconductors

• We have shown for the first time that one can evaluate hole and electron effective mass using only the band gap variation of degenerate semiconductors.
• We demonstrated that electron and hole effective masses in Aluminum doped ZnO thin films varies between 0.3m0 and 0.74m0 and −3.74m0 to −1.07m0, respectively when Al concentration changes between 2–10 %.
• We show that the increase of carrier concentration in Al doped ZnO thin films leads to increase and decrease of electron and hole effective masses, respectively.

In this study, the role of many-body interactions, Pauli blocking, and impurity-carrier interactions on the band gap variation were used to analyze the observed blue shift of the Al doped ZnO thin films. The optical constants and the band gap variations of our samples were obtained using spectroscopic ellipsometry method. Tauc-Lorentz model and effective medium approximation were used to model the dielectric function. We demonstrated for the first time that the combination of the Tauc formalism for absorption and the proposed model by Jain et al. for the band gap variation, can be used to determine both electron and hole effective masses. Reasonable results were obtained for carriers effective mass and their dependence on carrier concentration.