Enhancement of Light Output Power in InGaN/GaN LEDs with Nanoroughed Hemispherical Indium Tin Oxide Transparent Ohmic Contacts

The light output power of light emitting diodes (LEDs) has been enhanced using nanoroughed hemispherical indium tin oxide (ITO) transparent ohmic contacts. The hemispherical shape is easily achieved by evaporating ITO film on an ITO nanosphere, and the aspect ratio of an individual hemispherical ITO is determined by the size of the ITO nanosphere. The diameter of the ITO nanospheres can be easily controlled by controlling the thickness of the ITO films. The light extraction efficiency of InGaN/GaN LEDs is significantly improved due to light incident at an angle of approximately 90° at the hemispherical nanoroughed prominence–air interface. Also, a high surface area of ITO prominences increases the light extraction efficiency. Thus, the light output power of the nanoroughed hemispherical LEDs is increased by 30% compared to conventional LEDs at an injection current of 20 mA.