Temperature dependence of GaN Schottky diodes I-V characteristics

We have studied the temperature dependence of I-V curves of GaN Schottky diodes with two crystal polarities. Relatively large barrier height differences have been observed between Ga- and N-face GaN polarities which we ascribed to the possible influence of the surface fixed charge caused by the opposite spontaneous polarization in GaN with Ga- and N-polarities. Large differences between barrier height calculated from I-V and C-V curves may also be caused by the fixed surface polarization charge. Barrier heights decrease with decreasing temperature for both polarities and ideality factors increase. Low ideality factors and no excess leakage currents indicate thermionic transport mechanism for Ga-face diodes at temperatures over 200 K. On the contrary large ideality factors and reverse leakage currents for N-face polarity diodes are probably connected with other form of current transport-tunneling.