A comparative analysis of InAs quantum dot heterostructure with equal and varying sub-capping layer thickness using digital alloy approach

In current study, the variation of sub-capping thickness of InGaAs strain reducing layer (SRL) of InAs quantum dot heterostructure using digital alloy approach is presented. The thickness of 6 nm SRL of conventional structure (sample A) is divided equally with 2 nm thickness (sample B) by using digital alloy approach. Further, using such approach, this thick 6 nm capping is divided in unequal fashion for sample C (1 nm, 2 nm and 3 nm) and sample D (3 nm, 2 nm and 1 nm) from InAs QD towards top GaAs layer. The In-content inside the SRL of the sample A is 15%, whereas, In-content inside the divided-SRL is considered as 45%, 30% and 15% for all other samples. Such composition of SRLs helps in reducing the In-out diffusion, minimizing the lattice mismatch at InAs QD-SRL and SRL-top GaAs layer interfaces, and also reduces the strain inside the overall heterostructures. Two strains, namely hydrostatic and biaxial are calculated by using Nextnano for all the structures and compared simultaneously. The hydrostatic strain inside the QD of sample D is reduced by 4.74%, 1.07% and 2.269% and the biaxial strain inside the QD of sample D is improved by 1.66%, 0.696% and 1.276% as compared to that of samples A, B and C, respectively. The computed PL emission of samples A, B, C and D are observed to be 1305 nm, 1365 nm, 1349 nm and 1375 nm, respectively. Hence, sample D is the optimum choice for fabricating future opto-electronic devices.