Strain relaxation in InAs quantum dots through capping layer variation and its impact on the ultrafast carrier dynamics

Abstract

Ultrafast carrier dynamics is found to be crucial for influencing the efficiency of quantum dot (QD)-based optoelectronic devices. Here, we have studied picosecond resolved dynamics in InAs semiconductor quantum dots forming various heterostructure geometries with their different capping layers. The carriers (electron-hole pairs) are optically injected into three dimensional heterostructure barriers after which, we monitor the carrier relaxation into the zerodimensional InAs dots by using picosecond resolved time correlated single photon counting technique. We have explicitly investigated and analyzed the effect of three different capping layers, GaAs (binary), In 0.15 Ga 0.85 As/GaAs (ternary) and In 0.21 Al 0.21 Ga 0.58 As/GaAs (quaternary) offering various optical properties of InAs quantum dots. It has been observed that quaternary strain reducing layer effectively suppresses Indium migration from the QDs and enhances the confinement of carriers inside the QD heterostructures. In this study, we also find that thermal stability of the carriers is improved in the quaternary capped QDs more effectively compared to the conventional binary and ternary capped one. In brief, our experiments provide essential insight into carrier relaxation in the InAs QDs across various capping layers.

Exploring the Implementation of GaAsBi Alloys as Strain-Reducing Layers in InAs/GaAs Quantum Dots

“…The first SRL material used for InAs QD lasers was InGaAs [ 10 , 11 ], but other SRL materials have also been explored, such as InAlAs [ 12 ], GaAsSb [ 13 , 14 ], and quaternary compounds such as InGaAsN [ 15 , 16 ], InGaAsSb [ 17 ], GaAsSbN [ 18 , 19 ], or GaAsSb/GaAsN superlattices [ 20 ]. These SRLs can offer more flexibility in band structure design and other advantages such as avoiding In segregation [ 21 ], increasing the energy separation between the ground and excited states [ 22 ], suppressing QD decomposition [ 23 ], forming type-II band structures [ 24 , 25 ], and overall, extending the emission wavelength [ 7 , 9 ].…”