Quaternary – alloyed capping for strain and band engineering in InAs sub – monolayer quantum dots

Abstract

In the last few years, a considerable amount of attention has been given to the optimization of several capping layers (CLs) in InAs/GaAs sub – monolayer (SML) quantum dots (QDs) heterostructure for a sustainable room – temperature (RT) operation in 1.3–1.55 μm telecommunication range (O, C – bands). In particular, the quaternary – alloyed capping (Q – CL: Q – Sb: InxGa1−xAsySb1−y, Q – N: InxGa1−xAsyN1−y, and Q – SbN: GaAsxSbyN1−x−y) has been explored in this work to reach the above – stated photoluminescence (PL) emission wavelength and we compared it with the conventional InAs/InxGa1−xAs QDs using Nextnano software. This tool is based on 8 – band k.p model that solves the self – consistent Schrödinger – Poisson equations analytically to obtain the envelope functions of the eigen energy levels (both electrons and holes) and finally the absorption spectra. Although Q – CL help in preserving QD morphology by strain reduction, it also allowed us create deep carrier confinement potential near conduction and valence band offsets i.e. CBO (VBO) where there is a minimum carrier escape probability towards GaAs barriers (more thermal stability) thus fostering a prolonged PL emission wavelength at 300 K. By changing atomic constituent's composition in Q – CLs, the obtained ground – state (GS) band – to – band absorption energy are 1.31 (Q – Sb22%, 1.25 (Q – N1.8%), 1.37 μm (Q – SbN2.2%))). Such deep confinement aid in the dark current reduction and can promote for high temperature operation by improving the PL quantum yield by several orders of magnitude. The inherent material properties of CL composing the surfactant effect of Sb, larger bond strength of tensile – strained dil.N, and phase separation effects of Sb–N alloys are advantageous in this regard to corroborate further PL redshift.