Franz-Keldysh eect in epitaxial ZnO thin lms

J. F. FERREYRA; M. J. VILLAFUERTE; B. STRAUBE; G. NIEVA; J. GUIMPEL; C. A. FIGUEROA; G. BRIDOUX; S. PEREZ DE HELUANI

Simposio; XXIII Simposio Latinoamericano de Física del estado Sólido; 2018

Photoconductance spectroscopy has been studied in epitaxial ZnO thin lms with dierent thicknesses that range between 136 and 21 nm. We report a systematic decrease of photoconductivity and a red shift of the band edge photoconductance spectra when the thickness is reduced. For thinner lms, it is found that the eective energy gap value diminish. By time dependent photoconductivity measurements we found a lower contribution of theirslower characteristic relaxation times when thickness is diminished. These eects can be understood considering a band-bending contribution where the Franz-Keldysh eect and the polarization of the ZnO lms play a major role for thinner lms.