TEM investigations of (In,Ga)N/GaN quantum structures

Abstract

AbstractThe paper reports on the influence of the growth temperature on the structural and chemical properties of (In,Ga)N quantum wells (QWs) on GaN. Two different samples A and B were fabricated. The QWs of the sample A were grown at a constant temperature of 600 °C. For the QWs of the sample B the temperature was 530 °C, while for the GaN barrier it was raised to 600 °C. The chemical and structural properties were studied by electron diffraction contrast imaging using the 0001 and 0002 reflection, respectively. Sample A exhibits homogeneous (In,Ga)N QWs. For sample B some undulated strain contrast of the QWs is visible hinting to the formation of quantum dots (QDs). The self‐organisation of (In,Ga)N QDs in sample B is also evidenced by composition sensitive STEM‐HAADF imaging, where the individual (In,Ga)N layers exhibit inhomogeneous intensity as well as varied thickness. Moreover, energy dispersive X‐ray spectroscopy yielded enrichment of indium at QD sites. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)