Saturation of the photoresponse in Nd0.67Sr0.37MnO3−δ epitaxial layers close to the metal–insulator transition

Abstract Internal electrical fields of different origin are observed in the semiconducting regime of Nd 2/3 Sr 1/3 MnO 3− δ epitaxial layers and are assigned to thermoelectric effects and to an ambipolar charge distribution in trap states, following a photogeneration of electron–hole pairs. In particular, if the resistivity shows a double peak, the photoresponse shows saturation in the regime of the low-temperature peak, suggesting the existence of a gap in the transitional regime of the metal–insulator transition.