Photoelectronic properties of YBa2Cu3O6

Abstract

The photocurrent and luminescence properties of thin (1 μm) YBa2Cu3O6 films on sapphire at 77 and 300 K are reported. We demonstrate that the luminescence mechanism of YBa2Cu3O6 depends considerably on the wavelength of the excitation used. Completely different luminescence responses are observed with the 351 and 458 nm lines. A fair agreement, like that in semiconductors with band-to-band transitions, is found between photocurrent and luminescence excited by the 458 nm line. The influence of high electric fields (≤ 5 780 V cm−1) on the photocurrent and luminescence of YBa2Cu3O6 is investigated for the first time. Similar effects on photon-induced tunneling phenomena (Franz–Keldysh effect) are observed. However, we show that the observed effects cannot be explained by photon-induced tunneling phenomena only since the influence of an electric field on the band structure of YBa2Cu3O6 is not only restricted to a bending of bands but modifies the band structure in a more complex manner.