Strength of coherently strained layered superlattices

Abstract

Electronic-grade single-crystal semiconductor structures provide a means to study the mechanical effects of coherency strain in isolation. In this work, thin coherently strained InGaAs superlattices grown on thick InP substrates were tested in three-point bending at 500°C. The force-deflection curves of the specimens were measured and the beams were found to be significantly strengthened by the presence of the superlattices. Analysis provides estimates of the stress supported by the thin superlattices in the plastic regime. The superlattices are found to display mechanical strength up to a hundred times greater than the strength of the bulk substrate material. This effect can be attributed only to the coherency strain in the superlattices.

Acknowledgements

We thank Mark Hopkinson of the EPSRC Central Facility for III-V Semiconductors at Sheffield University for growing the samples used in this study.