Multicolour luminescence from InGaN quantum wells grown over GaN nanowire arrays bymolecular-beam epitaxy

Abstract

The luminescence of InGaN single quantum wells grown bymolecular-beam epitaxy under fixed conditions over a series ofc-axis GaN nanowire arrays with different geometrical parameters was studied. For arrayswith variable GaN average wire diameters and fixed wire densities, the InGaN luminescencepeak shifted to higher energy with decreasing wire diameter. It is shown that this trendcannot be attributed to lateral quantum confinement or diameter-dependent InGaN strain.For arrays with variable wire densities and fixed average diameters, the InGaN emissionappeared as two distinct bands of different colours, the relative intensities of whichdepended on the wire density. By optimizing both the GaN wire density and InGaN growthconditions, the colours of the two different bands were combined to realize phosphor-freewhite light-emitting diodes. The mechanisms for the dependence of the InGaNluminescence on the geometrical parameters of the GaN nanowire array are discussed.