Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 83: Oxide Semiconductors (joined session with CPP, DS)

HL 83.6: Talk

Friday, March 24, 2017, 11:30–11:45, POT 51

Tuning the refractive index of transparent conducting oxides via oxide/oxide periodic heterostructures — David Caffrey, Emma Norton, Cormac Ó Coileáin, Christopher M. Smith, Igor V. Shvets, and •Karsten Fleischer — School of Physics and CRANN, Trinity College Dublin, The University of Dublin, Ireland

Superlattice structures are a novel method of improving upon the optoelectronic properties of Transparent Conducting Oxide (TCO) structures. The invariability of the refractive index of TCO materials leads to reflection losses cells. The development of a transparent material or structure of tuneable refractive index at the interfaces of transparent devices such as solar would allow for the integration of anti-reflective coatings which would reduce such losses significantly, thus improving device efficiency. Previous attempts to modify the refractive index have been marred by the degradation of the electrical or optical properties of the tuned material. We demonstrate the novel use of a TCO/dielectric superlattice structure to achieve an effective medium of altered refractive index, while maintaining high values of transparency, conductivity and mobility. We demonstrate the efficacy of these superlattice structures on both amorphous InGaZnO₄ and ZnO:Al via TCO/SiO₂ and TCO/TiO₂ superlattices. The effective refractive indices of the films were successfully tuned over a range of Δ n≈ −0.2 (SiO₂ inclusion) to +0.4 (TiO₂ inclusion) with a decrease in conductivity of less than an order of magnitude. Mobility of the films was also well conserved. We also discuss differences in the carrier injection from the TCO into the dielectric for the SiO₂ and TiO₂ case.