Improvement of the light output and contact resistance of InGaN-based light-emitting diodes based on tantalum-doped indium tin oxide as p-type electrodes

This paper reports that highly transparent and low resistance tantalum-doped indium tin oxide (Ta-doped ITO) films contacted to p-type GaN have been prepared by the electron-beam evaporation technique. The Ta-doped ITO contacts become Ohmic with a specific contact resistance of \sim5.65\times 10^ - 5 \Omega \cdotcm^2 and show the transmittance of \sim 98% at a wavelength of 440~nm when annealed at 500 ^\circC. Blue light emitting diodes (LEDs) fabricated with Ta-doped ITO p-type Ohmic contact layers give a forward-bias voltage of 3.21 V at an injection current of 20 mA. It further shows that the output power of LEDs with Ta-doped ITO contacts is enhanced 62% at 20 mA in comparison with that of LEDs with conventional Ni/Au contacts.