InGaN-based light-emitting diodes grown on grooved sapphire substrates

We investigate the microstructure and electrical properties of the InGaN-based light-emitting diodes (LEDs) fabricated onto patterned sapphire substrates (PSSs) with parallel grooves. The PSS with parallel grooves (ridge: 3 urn; trench: 2 μm) along the (11-20) direction were etched using an inductively-coupledplasma etcher with different etching depths. It was found that the threading dislocation density in the GaN epilayer can be effectively reduced by the present PSS technique as indicated from the transmission- electron-microscopy result. For a typical lamp-form PSS LED operating at a forward current of 20 mA, the output power and external quantum efficiency were measured to be 7.1 mW and 10.1%, respectively. The achieved improvement of the output power is not only due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, but also due to the enhancement of the extraction efficiency using the PSS.