Structural and optical properties of shape-engineered InAs quantum dots in a GaAs matrix emitting at 1.27 μm

Shape-engineered InAs quantum dots (QDs) embedded in a simple GaAs matrix were grown by a molecular-beam epitaxy and investigated by cross-sectional transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Cross-sectional TEM images indicated that the shape of InAs QDs, especially height, was controlled only by introducing the periodic growth interruption of the indium supply during the growth of the QD layer (QDWGI sample). The emission wavelength for the QDWGI sample was 1.27 mu m, which is relatively longer compared to the InAs QDs formed without the growth interruption (reference QD). Also, the energy-level spacing between the ground states and the first excited states for the QDWGI sample was drastically increased to 73 from 54 meV of the reference QD sample. While the PL yield for the reference QD sample at room temperature was reduced by 1/142 from that measured at 18 K, the reduction in PL yield for the QDWGI sample was only 1/16. (c) 2007 Elsevier B.V. All rights reserved.