Hole conduction characteristics of cubic Ti1−xAlxN

Cubic Ti1−xAlxN (x = 0.5, 0.6) films were deposited using RF (radio frequency) magnetron sputtering and cathodic arc ion plating methods on a thermally oxidized Si substrate to evaluate the temperature dependence of their electrical characteristics by Hall measurements from 10 K to 295 K. The temperature dependence of the hole concentration and the electrical conductivity above about 200 K shows that cubic TiAlN in this study had semiconductor characteristics, indicating that the hole conduction in the valence band is dominant in a high temperature range above about 200 K. In contrast, the variable range hopping conduction is dominant in a low temperature range below about 100 K. In addition, the hole mobility of Ti0.4Al0.6N deposited by RF sputtering increased with increasing temperature above 220 K, even though the phonon scattering increases. This result shows that a disordered grain boundary between polycrystalline TiAlN acts as a barrier layer for the hole conduction.