Fabrication and efficiency improvement of micropillar InGaN/Cu light-emitting diodes with vertical electrodes

We present a micropillar surface structure based on the enhancement of the light extraction efficiency of the near-ultraviolet (409 nm) vertical-conducting InGaN light-emitting diode (LED) with an electroplated Cu substrate. The micropillar InGaN/Cu LED (chip size: 1x1 mm(2)) was fabricated using a combination of patterned sapphire substrate (PSS), laser lift-off, and copper electroplating processes. The PSS and Cu substrate can offer the advantages of dislocation reduction and thermal heat sink, respectively. It was found that the light output power (at 350 mA) of the micropillar InGaN/Cu LED sample can be improved by 39% as compared with that of the conventional InGaN/Cu LED one. This significant enhancement in output power could be attributed to the increase of the extraction efficiency which is a result of the increase in photon escaping probability caused by scattering the emission light at the micropillar surface. The light extraction efficiency can be further optimized by tuning the micropillar spacing, as evidenced by the ray-tracing simulation result. (c) 2006 American Institute of Physics.