The influence of atomic ordering on strain relaxation during the growth of metamorphic solar cells

18th Microscopy of Semiconducting Materials Conference

物理学;材料科学

Norman, A.G.^1 ; France, R.M.^1 ; McMahon, W.E.^1 ; Geisz, J.F.^1 ; Romero, M.J.^1

National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, United States^1

关键词: Antiphase boundaries;    Deleterious effects;    Direction of substrates;    Dislocation glide;    Ordered structures;    Strain relaxation mechanism;    Strain-relief buffer;    Threading dislocation densities;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/471/1/012006/pdf
DOI  :  10.1088/1742-6596/471/1/012006

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

The occurrence of single variant CuPtBordering during growth of InGaP graded buffer layer structures on offcut (001) GaAs substrates for inverted metamorphic solar cells is found to have a strong influence on strain relaxation mechanisms. Since the surface-induced CuPtB ordering is metastable in the bulk of the material, a strong preference is observed for the nucleation and glide of 60° type misfit dislocations with Burgers vectors that introduce an antiphase boundary into the ordered structure. This results in an overall epitaxial layer tilt in the opposite sense to that normally observed for the direction of substrate offcut. Furthermore, in InGaP buffer layers graded to InP, a switch in the dislocation glide plane preference back to that normally observed for the direction of substrate offcut is observed as the degree of atomic ordering falls below a critical value. This results in the nucleation and glide of new misfit dislocations resulting in an increase in the threading dislocation density that is found to have a deleterious effect on device efficiency. Understanding the materials science behind this behavior will enable the engineering of more effective, lower threading dislocation density strain relief buffer layers resulting in improved performance of subsequently grown devices.