Annealing effects on the electrical, structural and morphological properties of Ti/p-GaN/Ni/Au Schottky diode

Rapid thermal annealing effects on the electrical, structural and surface morphological properties of a fabricated Ti/p-GaN Schottky diode (SD) have been investigated. The AFM results showed that the surface morphology of the Ti/p-GaN SD is reasonably smooth at different annealing temperatures. The estimated Schottky barrier height (SBH) of the as-deposited and 200 °C annealed Ti/p-GaN SDs is found to be 0.88 eV (I–V)/1.02 eV (C–V) and 0.91 eV (I–V)/1.11 eV (C–V). Results showed that the SBH increases to 0.98 eV (I–V)/1.26 eV (C–V) upon annealing at 300 °C for 1 min in N2 ambient. However, the SBH slightly decreases to 0.94 eV (I–V)/1.17 eV (C–V) after annealing at 400 °C. Using Norde method and Cheung’s functions, the series resistance, SBH and ideality factor of the Ti/p-GaN SD are estimated and discussed at various annealing temperatures. Also, the difference between the SBHs calculated by I–V and C–V methods are discussed. Further, the interface state density N ss of the Ti/p-GaN SD is calculated and it is found to be decreases upon annealing at 300 °C and then slightly increases after annealing at 400 °C. Experimental electrical results are also correlated with the interfacial microstructure of the Ti/p-GaN SD. The SIMS and XRD results revealed that the increase or decrease in the SBHs of the Ti/p-GaN SD upon annealing could be attributed to the formation of Ti–N and Ga–Ti interfacial phases at the interface.