Effect of GaAs1-xNx capping layer on the strain profile and emission PL wavelength of InAs quantum dot heterostructures using digital alloy approach

Abstract

The impact of GaAs1-xNx as a capping layer of InAs quantum dots using digital alloy approach has been investigated. GaAsN capping layer helps in homogeneous distribution of dots on the surface due to formation of nitrogen induced point defects, which helps in minimizing overall compressive strain within the QDs and hence increased dot size. The capping layer of thickness 10 nm with nitrogen composition of 1.8% (Sample A) is considered for analog alloy or conventional approach. The short-period-superlattice (SPS) or sub-divided capping concept has been taken in digital alloy approach for depositing the capping layer. Each SPS is having 2.5 nm thickness and different nitrogen content (1.2%, 1.4%, 1.6%, and 1.8% in each SPS from QD towards top GaAs layer) (Sample D). The hydrostatic and biaxial strain have been computed using Nextnano simulation software and compared for both the mentioned approach. The hydrostatic and biaxial strain in sample D is improved by 0.329% and 0.093% respectively as compare to that in sample A. The observed emission PL wavelength is computed to be 1508 nm and 1430 nm for samples A and D respectively. The simulated PL of sample D is less as compare to that of sample A because of same dot size has been considered for simulation. But as we grow the digital sample using GaAsN material as capping layer, the dot size is increased which in turn helps in red shift in emission PL. Thus, digital alloy approach helps in making devices for future optoelectronic applications.