Misfit dislocation blocking by dilute nitride intermediate layers

Defect formation and strain relaxation in step-graded GaAs1-xNx and GaAs1-yPy buffer structures grown by metal-organic vapor phase epitaxy on GaAs(001) substrates have been investigated by transmission electron microscopy and high-resolution x-ray diffractometry. From the comparison of different buffer concepts, it is shown that, by introducing intermediate GaAs1-xNx layers with N concentrations x >= 2% into a GaAs1-xPx buffer structure, dislocation formation and strain relaxation are effectively suppressed during subsequent growth of layers with tensile strains. It is argued that a similar concept, however, modified by using layers of differing alloy composition, can be used for layer systems with compressive strains. Appropriately alloyed intermediate dilute nitride layers appear to offer a powerful concept for engineering defect distributions and layer strain in semiconductor technology. (C) 2008 American Institute of Physics.