InGaN Quantum Dot LEDs and lasers Grown by MOCVD

Abstract

Group III-nitride based quantum dots (QDs) have attracted considerable attention for optoelectronic device applications due to the strong quantum confinement. In this thesis, an investigation of self-assembled polar InGaN QDs on c-plane sapphire and Si substrates by metal-organic chemical vapor deposition (MOCVD) is reported. The short radiative exciton lifetime of 480 ps for uncapped QDs is much shorter than that for previously studied polar QDs and is even comparable with those grown along non-polar QDs. The photoluminescence intensity of the InGaN QDs is enhanced by using a novel vertically aligned and uniformly separated InGaN nanorods underneath. Furthermore, green-emission (512 nm) InGaN quantum dot LEDs grown on a c-plane sapphire substrate by MOCVD is demonstrated. These high quantum efficiency and high temperature stability green QD LEDs are able to operate with negligible efficiency droop and with current density increased up to 106 A/cm². Green InGaN QD microdisk lasers pivoted on Si substrate with the lowest measured threshold at a record low of 76 W∕cm² at room temperature under continuous-wave optical pumping was achieved.