A study was made of the effect of GaN buffer threading dislocation optimization and InGaN/GaN quantum well H2-treatment upon the efficiency of GaN light-emitting diodes operating in the spectral range of 400 to 500nm. A tenfold reduction of the threading dislocation density in the GaN buffer increased the efficiency of blue light-emitting diodes operating at high current density, while in green light-emitting diodes it had very little effect. The reduced threading dislocation density also increased the compressive strain in the InGaN quantum wells, and caused blue shift to the electroluminescence peak wavelength. The H2 treatment of the quantum wells increased strain inside the multi quantum-well stack. It was possible to apply the H2 treatment only to UV light-emitting diodes, as the increased strain in blue and green light-emitting diodes caused relaxation of the multi quantum-well stack. Although this resulted in smooth surface morphology of the multi quantum-well stack, it did not lead to any increase in the efficiency of the UV light-emitting diodes.

The Effect of InGaN/GaN MQW Hydrogen Treatment and Threading Dislocation Optimization on GaN LED Efficiency. S.Suihkonen, O.Svensk, T.Lang, H.Lipsanen, M.A.Odnoblyudov, V.E.Bougrov: Journal of Crystal Growth, 2007, 298, 740-3