Evolution of epilayer tilt in thick InxGa1-xAs metamorphic buffer layers grown by hydride vapor phase epitaxy

Tilt behavior in thick ln(x)Ga(1-x)As metamorphic buffer layers (MBLs) grown by hydride vapor phase epitaxy (HVPE) was measured by high-resolution reciprocal space mapping. Step-graded and continuously-graded structures, grown on nominally (001) oriented GaAs substrates, were analyzed. Tilt was measured as a function of position in a step-graded MBL. It was found that the tilt was strongest near the edges and tended to point toward the sample center. Step-grading induced a nearly linear tilt increase with x(InAs), while tilt increased slowly below x(InAs)similar to 0.10 then increased more sharply with In concentration in continuously-graded samples. The tilt behavior could be described by a model in which the tilt k attributed to imbalances in dislocations that result from cross-slip within a glide length of the sample edge. This finding implies that dislocation multiplication by cross slip is an important strain relief mechanism during the growth of these MBLs. Strategies for minimizing tilt in HVPE MBLs are discussed. (C) 2015 Elsevier B.V. All rights reserved.