Electrical properties and current transport mechanisms of the Au/n-GaN Schottky structure with solution- processed high-k BaTiO₃ interlayer

The electrical properties and current transport mechanisms of Au/BaTiO ₃ (BTO)/n-GaN metal-insulator-semiconductor (MIS) structures have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. Experimental results reveal that the MIS structure has a higher rectification ratio with low reverse leakage current compared with the Au/n-GaN metal-semiconductor (MS) structure. The calculated barrier height of the Au/BTO/n-GaN MIS structure [0.87 eV (I-V)/1.02 eV (C-V)] increases compared with the Au/n-GaN MS structure [0.73 eV (I-V)/0.96 eV (C-V)]. The series resistance is extracted using Cheung's functions, and the values are in good agreement with each other. Furthermore, the energy distribution of the interface state density is estimated from the forward-bias I-V data. It is noteworthy that the interface state density of the MIS structure is lower than that of the MS structure. In both MS and MIS structures under forward-bias conditions, ohmic and space-charge-limited conduction mechanisms are identified at lower and higher voltages, respectively. Investigations reveal that Poole-Frenkel emission dominates the reverse leakage current in both Au/n-GaN and Au/BTO/n-GaN structures.