Electrical, optical, and structural characteristics of ohmic contacts between p -GaN and ITO deposited by DC- and RF-magnetron sputtering

This paper reports the electrical, optical, and structural characteristics of ohmic contacts between p -GaN and indium tin oxide (ITO) deposited by DC and RF magnetron sputtering. Unlike the DC-sputtered ITO contacts, which showed non-linear current-voltage ( I–V ) behaviors irrespective of rapid-thermal annealing, the RF-sputtered ITO contacts become ohmic with increasing temperature up to 550°C under a N 2 ambience. In the wavelength region below 410 nm, the light-transmittance of the RF-sputtered ITO contact was somewhat higher than that of the DC-sputtered ITO before and after annealing. Oxygen-rich and oxygen-deficient structures were formed on the as-deposited DC- and RF-sputtered ITO surface, respectively. On the other hand, annealing gave rise to an oxygen-rich ITO surface for both ITO samples. Unlike the DC-sputtered ITO contact, the RF-sputtered ITO sample experienced an amorphous to polycrystalline phase transformation after annealing.