Schottky barrier properties of various metal (Zr, Ti, Cr, Pt) contact on p-GaN revealed from I-V-T measurement

Schottky barrier contact using three different metal (Zr, Ti, Cr and Pt) and Ohmic contact using Ni were made on same epitaxial growth layer of p-GaN. Measurements were carried out using current-voltage-temperature (I-V-T) in the range of 27-100°C. Under forward bias and room-temperature (RT), the ideality factors (η) were determined to be 2.38, 1.82, 1.51 and 2.63, respectively, for Zr, Ti, Cr and Pt. The Schottky barrier height (SBH) and effective Richardson coefficient A^** were measured through modified Norde plot as one of the analysis tools. Barrier heights of 0.84, 0.82, 0.77 and 0.41 eV for Zr, Ti, Cr and Pt, respectively, were obtained from the modified Norde plot. Schottky barrier heights of Zr, Ti, or Cr/p-GaN were also measured through activation energy plot, and determined to be in the same range (∼0.87 eV) and Pt at 0.49 eV. These results indicate that the Fermi level seems to be pinned due to the value of slope parameter (S) was very low (S = −0.25).