posted on 2022-09-02, 12:06authored byEamonn
T. Hughes, Mario Dumont, Yingtao Hu, Di Liang, Raymond G. Beausoleil, John E. Bowers, Kunal Mukherjee
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.