Growth behavior and defect reduction in heteroepitaxial InAs and GaSb on GaAs using block copolymer lithography

Defect reduction in heteroepitaxial growth of GaSb and InAs was achieved using nano-patterned GaAs substrates generated by block copolymer lithography (BCL). The lattice-mismatched growth of both GaSb and InAs on nano-patterned GaAs templates exhibited defect mitigation with few observed threading dislocations, but the growth behavior and surface morphology of the resultant films were very different for the two systems. The strain relaxation process proceeds through the relaxation of the nanoscopic, highly lattice-mismatched islands prior to film coalescence. The growth of GaSb on GaAs templates yielded a smooth, coalesced film whereas large islands were observed for the growth of InAs on such templates. The difference in surface morphology was described in terms of the interaction of adatom surface diffusion and the strain-dependent attachment of these atoms with the growing islands. The morphology can be altered through changes in growth temperature and rate. Nanolithographic patterning can be used as a general technique for integration of lattice-mismatched materials.