Investigations on the V-defect formation in GaInN-GaN multi quantum well structures

We investigate the relations between thickness and strain of GaInN-GaN MQW layers and the formation of defects. The samples were grown by MOPVE on sap phire or SiC substrates. We have deposited several GaInN-GaN MQW structures differing in thicknesses of both, GaInN well and GaN barrier material. We also produced MQWs grown at different temperatures and with different indiu m content. Scanning transmission electron microscopy images of such structu res revealed that the formation of V-defects is initiated by threading disl ocations. The generation of the defects always started at about the third q uantum well in the structure, irrespective of the average strain of the str uctures, which was changed through the mentioned variation of the well and barrier thicknesses. Moreover, we could not observe any significant variati ons in size or density of the V-defects with varying indium content or grow th temperature.