Dislocation Formation and Filtering in III–V Regrowth on GaAs Bonded on Si

Abstract

We develop a process to regrow thick III-As layers on a thin bonded template of GaAs on Si and uncover how to control the formation of threading dislocations. Such a hybrid approach potentially combines the advantages of full device wafer bonding and direct epitaxial growth for III–V optoelectronic integration on Si. One lingering challenge to this postbond regrowth technique, however, is thermal expansion mismatch between the film and substrate, leading to high dislocation densities when growing beyond the critical thickness. We find that the threading dislocation density of a simple 2.2 μm GaAs regrowth film rises as high as 8 × 106 cm–2, orders of magnitude higher than the original template density. Using compressively strained dislocation blocking layers, threading dislocation densities are reduced by as much as 30× down to 2.7 × 105 cm–2, and it is shown that, unexpectedly, most dislocations nucleate during cooldown following growth when the strain state reverses from compressive to tensile because of thermal expansion mismatch. Finally, potential design modifications are proposed to improve dislocation filtering efficacy and for growing device structures.