Impact of linear alloy on strain coupled bilayer InAs/GaAs1-ySby quantum dot heterostructures

In this work, the concept of the novel approach called linear alloy capping layer (LACL) has been investigated on the strain-coupled bilayer InAs/GaAs1-ySby QD heterostructures. Here, two analog structures with low (structure BA1) and high (structure BA2) antimony (Sb) contents, and one linear alloyed structure (BL) with varying Sb-content inside the capping layer is considered. The Sb-content inside the CL of structure BA1 and BA2 are 10% and 20%, respectively. Whereas, it is varying linearly from 20% to 10% inside structure BL. The CL and GaAs spacer layer thickness has been taken as 8 nm and 13 nm, respectively. All these three structures have been modeled using Nextnano++ simulation software. Two strain components, hydrostatic and biaxial have been computed and compared. These two strain components help in decreasing the ground state energy gap which leads to a red-shifted PL emission. The structure BL offers improved biaxial strain by 1.11% and 0.56% inside QD compared to structures BA1 and BA2. In addition, the magnitude of hydrostatic strain inside QD of structure BL is reduced by 1.78% and increased by 0.64% compared to structures BA1 and BA2. The strain inside the CL of structure BL is reduced very smoothly in a linear fashion as compared to other analog structures. The computed PL emission of structures BA1, BA2, and BL are 1371 nm, 1665 nm, and 1617 nm, respectively. Also, the proposed structure BL offers a type-II band profile. Hence this proposed approach is useful for future optoelectronic applications.