A novel transparent ohmic contact of indium tin oxide to n-type GaN

A novel transparent indium tin oxide (ITO) ohmic contact to n-type GaN (dopant concentration of 2 × 1017 cm−3) with a specific contact resistance of 4.2 × 10−6 Ω cm2 has been obtained. The interfacial properties involving with ITO to n-GaN ohmic contact are different from those of previous reported. Conventionally, ITO films were prepared using electron-beam evaporator and a Schottky contact was thereafter obtained with a barrier height of 0.68 eV. Moreover, the barrier heights increased in response to the rise of annealing temperature. However, in our studies we relied on different deposition technique instead by sputtering the ITO films onto n-type GaN using a RF sputtering system and in result I-V curve revealed a linear behavior. By increasing the annealing temperature to 600 °C, the ohmic contact resistance appeared to be in sharp decline. Possible explanations these phenomena were attributed to the surface oxide layer removal and N vacancies present on GaN surface, which occurred during the ITO sputtering.