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

• Electrical transport properties of doped In2O3 thin films are studied.
• Grain boundaries influence transport properties even at highest carrier concentrations.
• Advanced method for determination of grain boundary barrier height used.
• The commonly used Sn dopant of In2O3 is not ideal.
• Sn segregates to grain boundaries.

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 EB 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 EB 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.