Electronic high temperature characteristics of AlN

The high temperature electronic properties of bulk single crystal AIN were investigated by temperature dependent I-V measurements in the range of R.T. to 1100degC in vacuum. The samples have been highly insulating at R.T. Such isolation properties are mostly obtained by a high defect density and a high oxygen content. Temperature cycling was used to identify carrier activation and heterogeneous conduction paths possibly originating from a dislocation network. Indeed an increase in conductivity with temperature is observed, which can be fitted with an activation energy of 1.3 eV at medium temperatures. The crystals remained stable up to 1100degC. No change of the room temperature conductivity was observed after several cycles. Impedance spectroscopy at medium temperature, where the material behaves like a lossy dielectric, shows only one dominating conduction path. No grain boundary-like heterogeneous transport through a dislocation network could be detected. Thus, the materials´ quality as indicated by its Raman spectrum is also mirrored in the electrical high temperature performance