General mobility and carrier concentration relationship in transparent amorphous indium zinc oxide films

Abstract

We report the dependence of the electronic properties on the metal composition and oxygen content of transparent conducting amorphous indium zinc oxide $(a\text{\ensuremath{-}}\mathrm{IZO})$ films deposited by dc magnetron sputtering. $a\text{\ensuremath{-}}\mathrm{IZO}$ shows a clear Burstein--Moss shift with an effective optical band gap of $3.1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ independent of the metal composition. A metal-composition-independent dependence of the mobility $(\ensuremath{\mu})$ on carrier concentration $(N)$ is also found for $a\text{\ensuremath{-}}\mathrm{IZO}$ with ${\ensuremath{\mu}}_{\mathrm{max}}=54\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{2}∕\mathrm{V}\phantom{\rule{0.2em}{0ex}}\mathrm{s}$ at $N=1.3\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. The electron transport, thermally activated at $N\ensuremath{\leqslant}{10}^{19}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, becomes limited by lattice scattering at $N\ensuremath{\approx}{10}^{20}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ and then by ionized impurity scattering at $N>5\ifmmode\times\else\texttimes\fi{}{10}^{20}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$.