Electrical and structural characterization of InAs/InGaAs quantum dot structures on GaAs

abstract In this work we present the results of an electrical and structural characterization of molecular beamepitaxy (MBE) grown InAs/In 0.15 Ga 0.85 As quantum dot (QD) structures having InAs coverages of 2.0 and3.0ML that are, respectively, below and above the expected critical value for QD ripening in the InAs/GaAssystem. The samples have been investigated by atomic force microscopy (AFM), transmission electronmicroscope (TEM), capacitance–voltage ( C – V ), and deep level transient spectroscopy (DLTS) techniques.The results obtained by the above techniques are compared and discussed.© 2008 Elsevier B.V. All rights reserved. 1. Introduction In recent years, optoelectronic devices based on semiconductorquantum dots (QD) structures have been of great interest becauseoftheirpromisingtechnologicalapplications[1,2],suchasdevelop-ment of lasers that emit in the 1.3 and 1.55!m telecommunicationbands.BytheuseofselfassembledInAsQDgrownonmetamorphicInGaAs confining layers the emission over these wavelength rangescould be achieved [3]. One of the approaches to tune the emissionof InAs/InGaAs QD nanostructures towards longer wavelengths isthe increase of InAs coverage to enlarge the QD size. However theincrease of InAs coverage beyond a critical value is expected toresult in QD ripening [4], as it has been reported in previous stud-ies on InAs/GaAs QD structures [5].Neverthelessdetailedstudieson the ripening effects in InAs/InGaAs QD structures have not yetbeen reported. In this work we present the results of an electricalandstructuralcharacterizationofInAs/In