Substrate orientation dependence of lateral composition modulation in (GaP)n(InP)n strained short period superlattices grown by gas source MBE

(GaP)₁(InP)₁ superlattices (SLs) were grown on GaAs (100), (311), (411) and (lll)B substrates by gas source MBE. Atomic force microscopy and transmission electron microscopy observations show that the SLs grown on GaAs (100), (311)A and (411)A substrates have wire, wire-like and dot-like lateral composition modulations, respectively. 4.2K photoluminescence peak energies are greatly dependent on the substrate orientation and growth temperature, ranging from 1.722 eV to 1.979 eV. The lowest peak energy ever reported, 273 meV lower than that of the disordered InQ.5Gao.5P alloy, is observed from the SL grown on GaAs (111)B substrate, where the strong CuPt-type ordering is confirmed.