Extraction-efficiency enhancement of InGaN-based vertical LEDs on hemispherically patterned sapphire

摘要

To improve the external quantum efficiency, a vertical type InGaN LED (VT-LED) is fabricated on a sapphire substrate with a surface hemispherically-patterned by laser lift-off (LLO) technique. As a result, the VT-LEDs with a concavely patterned surface revealed an enhanced luminous intensity by four times compared to the device with a planar surface. This improvement in the VT-LED performances is explained to be attributed mainly to the increase in the escaping probability of photons due to the corrugated LED surface. The use of metallic substrate prepared by nickel electroplating seems the other factor for the increase of luminous intensity by considering reduced current crowding and better thermal conductivity. These devices are advantageous for high power operation.