InGaN/GaN Quantum Dot Light-Emitting Diodes on Silicon with Coalesced GaN Nanowire Buffer Layer

Abstract

We demonstrate InGaN/GaN quantum dot light-emitting diodes on silicon substrates with a planar buffer layer formed by coalescing GaN nanowires. The GaN buffer layer and the light-emitting diode heterostructure were grown by plasma-assisted molecular beam epitaxy. The coalesced nanowire layer exhibits a defect density of the order of ∼109 cm2, a root-mean-square (rms) surface roughness of 0.562 nm, and excellent photoluminescence characteristics. Multiple layer In0.23Ga0.77N/GaN quantum dot light-emitting diodes grown and fabricated on the GaN/Si buffer layer exhibit strong electroluminescence at ∼477 nm with a very small blue shift of ∼2.4 nm, translating to a polarization field of ∼50 kV/cm, over the injection range applied. A droop is observed in the efficiency of the devices beyond an injection of 40A/cm2, most possibly due to defect-assisted Auger recombination and carrier leakage from the active region.