Investigation of the Impact of Point Defects in InGaN/GaN Quantum Wells with High Dislocation Densities

In this work, we report on the efficiency of single InGaN/GaN quantum wells (QWs) grown on thin (<1 mu m) GaN buffer layers on silicon (111) substrates exhibiting very high threading dislocation (TD) densities. Despite this high defect density, we show that QW emission efficiency significantly increases upon the insertion of an In-containing underlayer, whose role is to prevent the introduction of point defects during the growth of InGaN QWs. Hence, we demonstrate that point defects play a key role in limiting InGaN QW efficiency, even in samples where their density (2-3 x 10(9) cm(-2)) is much lower than that of TD (2-3 x 10(10) cm(-2)). Time-resolved photoluminescence and cathodoluminescence studies confirm the prevalence of point defects over TDs in QW efficiency. Interestingly, TD terminations lead to the formation of independent domains for carriers, thanks to V-pits and step bunching phenomena.

Automated summary

By inserting an In-containing underlayer during the growth of InGaN quantum wells (QWs) on thin GaN buffer layers, the emission efficiency of the QWs on silicon substrates is significantly increased. This study also reveals the crucial role of point defects in limiting the efficiency of InGaN QWs, even with a lower density compared to threading dislocations.