Manipulation of the structural and optical properties of InAs quantum dots by using various InGaAs structures

Abstract

The structural and optical properties of self-assembled InAs quantum dots (QDs) with various InGaAs structures were investigated by transmission electron microscopy (TEM) and photoluminescence (PL). The emission peak position of InAs QDs covered by a 6 nm In0.15Ga0.85As layer was 1.26 μm with PL linewidth of 31 meV, which is narrower than that of QDs in a GaAs matrix. By inserting a 1 nm In0.15Ga0.85As layer below the InAs QD layer with a 6 nm In0.15Ga0.85As overgrowth layer, the emission peak position was redshifted with larger energy-level spacing between the ground states and the first excited states compared to that of QDs with an In0.15Ga0.85As overgrowth layer only. By covering the InAs QDs on a 1 nm In0.15Ga0.85As layer with an 8 nm InxGa1−xAs layer having graded In composition, the emission peak position was 1.32 μm with relatively larger energy-level spacing and narrower PL linewidth compared to QDs covered by an In0.15Ga0.85As layer. The longer emission wavelength with relatively larger energy-level spacing was largely related to the change in the QD shape and size, especially the aspect ratio (height/width), which was confirmed by cross-sectional TEM images.

Capping of InAs/GaAs Quantum Dots for GaAs Based Lasers

“…Electroluminescence and lasing from the ground state at 1300 nm was achieved on quantum dot structures with InGaAs strain reducing layer prepared by molecular beam epitaxy (Liu, 2004) since this technology allows one to grow structures at lower temperature which decrease the In segregation and diffusion and improves localization of electrons in quantum dots. The localization of electrons in dots can be further improved by graded composition of InGaAs (Kim, 2003) or by combining the InGaAs strain reducing layer with InAlAs (Kong, 2008). Unfortunately, graded InGaAs composition is difficult to achieve when metal-organic vapour phase epitaxy is used for structure growth due to high In segregation during capping (Steimetz, 1998).…”

“…The most common capping materials used for the reduction of strain inside dots are InGaAs (Dasika et al, 2009;Kim et al, 2003) and GaAsSb (Haxha et al, 2009;Bozkhurt et al, 2011;Ulloa et al, 2007;Akahane et al, 2004), sometimes InAlAs or some combination of these materials is used (Liu et al, 2005;Kong et al,2008). Strain reducing layers covering InAs dots are used to shift the emission wavelength to 1.3 µm and 1.55 µm, typical of optical fibre communication.…”

Optical Properties of Multi-Stacked InAs Quantum Dots Embedded in GaAs/InGaAs Strained Layer and its Annealing Behaviors

“…Over the past several years, a three-dimensional quantum-confined structure, quantum dot (QD), has attracted considerable interest from both fundamental physics and potential device applications [1][2][3][4][5][6]. For example, a QD laser diode is expected to have high thermal stability, a low threshold current density, and a high gain due to the unique properties of QDs, atomic-like electronic states, and a delta-function-like density of states.…”

“…However, InAs/GaAs QDs grown via S-K growth method revealed large inhomogeneous broadening in the optical emission ranging from 50 to 90 meV. In order to achieve high uniformity in QDs size and shape, various growth parameters such as growth temperature, deposition rate, growth interruption group III/V ratio strain, and composition of structure layers, which affect the QD structures and their * corresponding author; e-mail: jyleem@inje.ac.kr optoelectronic properties, have been employed so far in lots of researches [5,[8][9][10].…”

Influence of InAs Coverage on Transition of Size Distribution and Optical Properties of InAs Quantum Dots

“…Various fabrication techniques have been proposed to realize a zero-dimensional structure of QDs, but most of them require complex fabrication processes. Among the QD fabrication techniques, self-assembled QD growth through the Stranski-Krastanov (S-K) mode has thus far provided the most prominent way to fabricate optoelectronic devices such as laser diodes and light-emitting diodes [4].…”