A novel approach for the complete removal of threading dislocations from ZnSe on GaAs (001)

Here we demonstrate a novel approach to the complete removal of threading d islocations in ZnSe on GaAs (001). This approach, which we call patterned h eteroepitaxial processing (PHP), involves post-growth patterning and therma l annealing. Expitaxial layers of ZnSe on GaAs (001) were grown to thicknes ses of 2000-6000 Angstrom by photoassisted metalorganic vapor phase epitaxy (MOVPE). Following growth, layers were patterned by photolithography and t hen annealed at elevated temperatures under flowing hydrogen. Threading dis location densities were determined using a bromine/methanol etch followed b y microscopic evaluation of the resulting etch pit densities. We found that as-grown layers contained more than 10(7) cm(-2) threading dislocations. T he complete removal of threading dislocations was accomplished by patternin g to 70 mum by 70 mum square regions followed by thermal annealing for 30 m inutes at temperatures greater than 500 degreesC. Neither post-growth annea ling alone nor post-growth patterning alone had a significant effect. The e ffectiveness of this approach diminishes significantly below 500 degreesC s o that annealing at 400 degreesC produces no measurable effect. We propose that the underlying mechanism for dislocation removal is the thermally acti vated glide of dislocations to the sidewalls of patterned regions, as promo ted by sidewall image forces.