Metamorphic buffers and optical measurement of residual strain

We show that the residual strain occurring in constant-composition metamorphic buffer layers of III-V heterostructures can be accurately predicted by the suitable design of the epitaxial structures and measured all optically by means of photoreflectance spectroscopy. This result allows one to single out the nonequilibrium models among those that have been proposed to predict strain relaxation. The resulting proportional to t(-1/2) dependence of the residual in-plane strain on buffer thickness t can be used to design metamorphic buffers not only for 1.3-1.55 mu m emitting quantum dot structures, but also for sophisticated graded-composition metamorphic structures for different classes of devices.