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Metamorphic semiconductor devices often utilize compositionally-graded buffer layers for the accommodation of the lattice mismatch with controlled threading dislocation density and residual strain. Linear or step-graded buffers have been used extensively in these applications, but there are indications that sublinear, superlinear, S-graded, or overshoot graded structures could offer advantages in the control of defect densities. In this work we compare linear, step-graded, and nonlinear grading approaches in terms of the resulting strain and dislocations density profiles using a state-of-the-art model for strain relaxation and dislocation dynamics. We find that sublinear grading results in lower surface dislocation densities than either linear or superlinear grading approaches.

Metamorphic semiconductor devices often utilize compositionally-graded buffer layers for the accommodation of the lattice mismatch with controlled threading dislocation density and residual strain. Linear or step-graded buffers have been used extensively in these applications, but there are indications that sublinear, superlinear, S-graded, or overshoot graded structures could offer advantages in the control of defect densities. In this work we compare linear, step-graded, and nonlinear grading approaches in terms of the resulting strain and dislocations density profiles using a state-of-the-art model for strain relaxation and dislocation dynamics. We find that sublinear grading results in lower surface dislocation densities than either linear or superlinear grading approaches.