Influence of dopant species and concentration on grain boundary scattering in degenerately doped In₂O₃ thin films

The influence of dopant species and concentration on the grain boundary scattering of differently doped In₂O₃ thin films is studied by means of room temperature and temperature dependent Hall effect measurements. Barrier heights at grain boundaries E_B are evaluated from temperature dependent carrier mobility taking the theoretically calculated temperature dependence of intragrain mobility into account. It is thereby shown that also samples with a negative temperature coefficient of mobility exhibit significant grain boundary barrier heights and that E_B is usually underestimated when evaluated based on Seto's model. It is also shown that the most commonly used Sn doping of In₂O₃ with a dopant concentration > 2 wt . % SnO₂ leads to significantly enhanced grain boundary scattering compared to nominally undoped, Zr-doped and H-doped films. An effect of grain boundary scattering is even observed for carrier concentrations ~ 10²¹ cm^− 3 if the films exhibit a pronounced (100) texture. The poor grain boundary properties of highly Sn-doped In₂O₃ are attributed to segregation of the Sn dopants, which is also indicated by measurements of surface Sn concentration.