Non-parabolicity and band gap re-normalisation in Si doped ZnO

A combinatorial methodology, developed for the rapid optimisation of sputtered transparent conducting oxides, was applied to Si doped ZnO. A wide range of compositions have been explored over a single sample to determine an optimum composition, with respect to the minimisation of resistivity, of x = 0.65% wt. SiO2. A fundamental investigation of the conduction band non-parabolicity yields values of m(e0) = 0: 35m(0) and C = 0.3 eV(-1) for the conduction band minimum effective mass and the non-parabolicity factor, respectively. The variation of extracted band gap values with respect to dopant concentration provided an estimate of the magnitude of re-normalization effects. A model is proposed to describe the carrier transport behaviour for a degenerate polycrystalline semiconductor by accounting for the tunnelling of carriers through grain boundaries. (C) 2014 AIP Publishing LLC.