Abstract
We show that Raman scattering is a sensitive technique for probing the degree of Ga intermixing in In(Ga)As∕GaAs self-assembled quantum dots (QDs). The shifts of the QD phonon frequency that we observe are explained by the modification of the strain due to Ga incorporation into the QDs from the GaAs matrix during growth. Using an elastic continuum model, we estimate the average In content of the dots from the QD phonon frequency. The varying amount of intermixing in QDs grown with different In compositions, QD layer thicknesses, growth temperatures, and stacking spacer layer thicknesses are investigated. The Raman data indicate that Ga intermixing is larger for QD samples with low In(Ga)As coverage thickness and∕or high growth temperature and, in multilayered systems, for samples with small GaAs spacer layers.
Highlights
Semiconductor quantum dotsQDsare of great interest both from a technological and a fundamental point of view
We focus on the following structures: ͑itwo series of single layers of InAs/ GaAs and InxGa1−xAs/ GaAs QDs grown with different coverage thicknesses; ͑ii InAs/ GaAs QDs grown at different growth temperatures; andiiia series of InAs/ GaAs stacked QDs with different spacer layer thicknesses
Probing the actual QD composition is difficult, and for InAs/ GaAs SAQDs Ga fractions of about 30% and higher were derived from scanning tunneling microscopy3 and from the analysis of the x-ray intensity distribution in reciprocal space
Summary
Semiconductor quantum dotsQDsare of great interest both from a technological and a fundamental point of view. Due to the strong three-dimensional3Dconfinement of carriers in QDs, these nanometer-size structures can be regarded as artificial atoms, providing a range of interesting physical phenomena and great potential for device applications. A thin layer of the deposited material, known as the wetting layerWL, is left under the SAQDs. The fabrication process ends with the capping of the islands so that the resulting QDs are surrounded by a matrix of larger band gap material. Since the self-assembly process removes the need for lithography and etching to obtain the dots, SAQDs have received much attention in the last few years and different systems have been developed and studied. InAs/ GaAs and InxGa1−xAs/ GaAs SAQDs have been widely investigated because of their applications to GaAs-based optoelectronic devices operating in the 1.3– 1.5 m range relevant for optical fiber communications.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
