Improved structural and optical behaviour of InAs Stranski-Krastanov (SK) quantum dot heterostructures using analog, digital, and linear alloy techniques

Abstract

In this study, we minimize the strain by using the new technique called linear alloy technique (LAT) for the Stranski-Krastanov (SK) quantum dot heterostructure. Here, three different SK InAs QDs heterostructures with 6 nm thick capping layer (CL) having In_xGa_1-xAs as capping material have been simulated using the 8-band k.p. model-based Nextnano software. Here, the first sample is analog alloyed SK QDs heterostructure having In_0.15Ga_0.85As capping (Sample A1), the second sample is digital alloyed SK QDs heterostructure where CL is divided into three sub-layers each of 2nm thickness with indium composition varied from 45-30-15% (Sample D1), and the third sample is linear alloyed SK QDs heterostructure where indium composition is varied from 45% to 15% (Sample L1) in a linear fashion, have been studied. The biaxial and hydrostatic strain is computed for all three heterostructures and compared. The biaxial strain is improved by 2.03% and 2.0%, and hydrostatic strain is reduced by 3.49% and 0.071% inside the QD region of sample L1 compared with samples A1 and D1, respectively. Additionally, digital sample D1 offers a step-wise strain reduction inside CL compared to analog sample A1. However, sample L1 offers an even more relaxed strain inside CL than samples A1 and D1, respectively. The PL emission wavelength is observed at 1317, 1372, and 1379 nm for samples A1, D1, and L1, respectively. Hence the linear alloy technique is useful for making future optoelectronic devices where strain reduction is the main factor.