Shallow trenches were etched into a substrate of n-type GaAs, off-cut from the [001] normal by 5° in both of the perpendicular [110] directions, before growing a lattice-mismatched layer of In0.035Ga0.965As. Scanning cathodoluminescence images showed that the misfit dislocations that form in order to relieve strain were reduced in density to less than 1700/cm, as compared with the over 5000/cm in unpatterned material. The off-cut substrate ensured that the 60° dislocations were no longer parallel, and could intersect and react to form edge dislocations. These interactions were observed as abrupt changes in line direction and contrast in cathodoluminescence images. The edge dislocations formed were up to 18µm long, and about 2µm below the wafer surface, until they split again into the original 60° defects. The shape and dimensions of these unique dark-line features were in qualitative agreement with calculations based upon simple strain-energy considerations.

Misfit Dislocation Interactions Observed by Cathodoluminescence in InGaAs on Off-Cut, Patterned GaAs. G.P.Watson, D.G.Ast: Journal of Applied Physics, 2003, 94[3], 1513-7