Structural properties of ultrathin InGaN/GaN quantum wells

A high indium-content blue light-emitting diode (LED) structure grown on silicon (111), consisting of five very thin MOCVD-grown In0.2Ga0.8N quantum wells (QWs), is shown by high resolution transmission electron microscopy (HRTEM) to contain structural defects in the active region. HRTEM imaging reveals QWs containing stacking faults and also gaps ranging between 5 nm and 50 nm in length which isolate separate regions of QW of similar dimensions to the gaps. The relatively high internal quantum efficiency of the structure is attributed to enhanced confinement of carriers via the ultrathin QWs, the strained sections of QW between the gaps, and by the sections of QW with sphalerite crystal structure, identified by characteristic stacking fault phase contrast in HRTEM images. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)