Enhanced luminescence and optical performance through strain minimization in self-assembled InAs QDs using dual quaternary-ternary/ternary-quaternary capping

Abstract

Theoretical simulations are necessary to scientifically progress, envisage and gain the first hand knowledge of the properties of semiconductor quantum dot (QD) structure. The impact of dual ternary-quaternary/quaternary-ternary capping layers on the square based truncated pyramidal InAs QD and their influence on the energy band structure as well as the strain profile has been investigated in this study. A comparative analysis has been demonstrated with binary, ternary and quaternary capping layer counterparts. The capping layers are: GaAs (binary), InGaAs/GaAs (ternary), InAlGaAs/GaAs (quaternary), InGaAs/InAlGaAs/GaAs (dual ternary-quaternary) and InAlGaAs/InGaAs/GaAs (dual quaternary-ternary). The hydrostatic and biaxial strain for all the heterostructures have also been computed and compared. The biaxial strain was highest for the QD capped with InAlGaAs/GaAs and InAlGaAs/InGaAs/GaAs, leading to the red shift of the ground state emission in the photoluminescence (PL) spectrum. The possible absorption peaks were also calculated for all QDs from the electron (EL) and hole (HL) eigenstates. The lowest energy transition (EL1-HL1) at 300 K is near to the communication wavelength for the optimum (InAlGaAs/InGaAs/GaAs capped) QD, which is at 1.35 µm. The optimized QD heterostructure claimed the highest electrostatic potential of 0.4986 V. This study will be helpful in predicting few optical and electrical characteristics based on the strain distribution inside the structure. The optimized QD structure having a consistent strain profile inside it would render superior luminescence characteristics. Finally, to verify the accuracy of the simulation, the simulated transition peaks at 19 K and 300 K were validated with the experimental PL data, and the percentage error was within 5%.