In situ curvature monitoring for metal–organic vapor phase epitaxy of strain-balanced stacks of InGaAs/GaAsP multiple quantum wells

Strain-balanced growth of highly mismatched quantum wells is of crucial importance for obtaining high performance devices such as quantum-well solar cells and quantum cascade lasers. In situ curvature measurement successfully captured strain accumulation in lattice-mismatched InGaAs/GaAsP multiple quantum wells that were grown by metal–organic vapor phase epitaxy. Average strain in the layers was detectable using the slope of curvature versus layer thickness. High-sensitivity measurement made it possible to detect strain accumulation and release within a single layer of InGaAs and GaAsP, respectively, by looking at the see-saw-like oscillation of curvature, which is an indication of successful strain balancing in a period of well/barrier. In situ curvature monitoring makes it easier and more efficient to adjust growth conditions for perfect strain balancing, as compared with conventional repetition of growth and X-ray diffraction measurement.