Misfit dislocations in In-rich InGaN/GaN quantum well structures

Abstract

Strain relaxation has been studied for the 10-period quantum well (QW) heterostructures grown by MOVPE, In 0.16Ga 0.84N/GaN and In 0.2Ga 0.8N/GaN, both emitting with high efficiency in the blue and green regions, respectively. Additionally, a set of high-In content InGaN/GaN QW structures, where growth parameters were kept constant but QW numbers varied between 1 and 10, were also analysed by TEM, XRD and PL. For the highly-efficient green and the set of variable QW samples, TEM structural studies identified large well-width fluctuations and misfit dislocations that thread into the sample surface and are generated in the quantum well stack. This contrasts with similar observations of blue-emitting MQWs where misfit dislocations are not seen. PL measurements have been carried out for the In-rich QW series and did not reveal a greater degradation of the optical properties with increasing numbers of quantum wells in the stack. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.