In situ HREM study on the thermal stability of atomic layer epitaxy grown InAs/GaAs quantum dots

Abstract

Self-assenibled InAs/GaAs quantum dots (QDs) were grown by the atomic layer epitaxy technique and the structure and the thermal stability of QDs have been studied by using high resolution electron microscopy with in-situ heating experiment capability. The QDs were found to form a hemispherical structure with ( 136) side facet in the early stage of growth. The average height and diameter of the QD were found to be similar to 5.5 nm and similar to 23 nm, respectively. Upon capping,by GaAs layer, however, the apex structure of QD changed to a flat one. In-situ heating experiment within, TEM revealed that the uncapped QD remained stable until 580 degrees C. However, at temperature above 600 degrees C, the QD structure became flat due to the fast decrease of QD height. After flattening, the atoms diffused from the InAs QD to the GaAs substrate, resulting in the total collapse. The density of the QD decreased abruptly by this collapse and most QDs disappeared at above 600 degrees C.