Vertical InGaN-based blue light emitting diode with plated metal base fabricated using laser lift-off technique

摘要

A vertical InGaN-based blue light emitting diode (LED) with a reflective metal electrode and thick gold plated base free from insulating sapphire is demonstrated. A 50 μm-thick gold plated layer on a highly reflective platinum p-side ohmic contact is formed on the InGaN-based LED epi-structure, followed by irradiation with high power ultra-violet pulsed laser from the backside of the original sapphire substrate. The laser processing, so called laser lift-off technique, enables the separation of sapphire by decomposition of interfacial GaN layer. No transparent electrode is necessary for the LED because the current can spread well through the highly conductive n-GaN layer so that uniform blue light is emitted through the n-GaN layer. The electroluminescence (EL) spectra show small multi peaks due to the resonance within the formed vertical cavity. In addition, the measured thermal resistance of the vertical LED is smaller than that of the conventional LED on poor heat-conductive sapphire. The vertical LED would increase the brightness together with smaller chip size and lower series resistance. This would be advantageous espa-cially for high power and highly efficient LEDs applicable to future solid state lighting.