Strain-relaxed buffer technology based on metamorphic InxAl1-xAs

• Residual strain of graded InAlAs layer was not affected by growth temperature.
• Epilayer tilt in forward-graded InAlAs only was not affected by growth temperature.
• Significant epilayer tilt was observed when inverse-grading was used in InAlAs.

A strain-relaxed buffer (SRB) technology that produces close to fully relaxed InxAl1–xAs is reported. The InxAl1–xAs layer was linearly graded from x=0.05 to 0.21. The effect of growth temperature on strain relaxation and surface morphology of InxAl1–xAs layer was studied here. For the strain relaxation study, the residual strain of InxAl1–xAs was measured with (004) and (224) reciprocal space maps along two orthogonal <110> directions. Atomic force microscopy was used to study the changes in surface roughness with growth temperatures. An InxAl1–xAs top-layer with 99.2% mean strain relaxation, surface roughness of 1.46 nm in root-mean-square (RMS) value, and a small epilayer tilt of 0.2° was attained when an inverse-graded layer strategy was employed. The remaining strain was anisotropic with +0.27% and −0.27% residual strains in the [1¯10] and [110] directions, respectively.