A study was made of the growth of crack-free blue and green-emitting light-emitting diode structures grown onto 2 and 6in Si(111) substrates by metal-organic vapour phase epitaxy, using AlN nucleation layers and AlGaN buffer layers for stress management. Light-emitting diode device performance and its dependence on threading dislocation density and emission wavelength were studied. Despite the inherently low light extraction efficiency, an output power of 1.2mW at 50mA was measured from a 500μm square planar device, emitting at 455nm. The light output decreased dramatically as the emission wavelength increased from 455 to 510nm. For light-emitting diode devices emitting at similar wavelength, the light output was more than doubled when the threading dislocation density was reduced from 5 x 109 to 2 x 109/cm2. The results clearly showed that high threading dislocation density was detrimental to the overall light output, highlighting the need for further threading dislocation reduction for structures grown on Si.

InGaN/GaN LEDs Grown on Si(111): Dependence of Device Performance on Threading Dislocation Density and Emission Wavelength. D.Zhu, C.McAleese, M.Häberlen, C.Salcianu, T.Thrush, M.Kappers, A.Phillips, P.Lane, M.Kane, D.Wallis, T.Martin, M.Astles, C.Humphreys: Physica Status Solidi C, 2010, 7[7-8], 2168–70