Investigation of MBE-grown InAs1−xBix alloys and Bi-mediated type-II superlattices by transmission electron microscopy

The microstructure of InAs1−xBix (x~4.5% and ~5.8%) films and Bi-mediated InAs/InAs1−xSbx type-II superlattices grown by molecular beam epitaxy on GaSb (0 0 1) substrates has been investigated by electron microscopy techniques. Lateral compositional modulation exists in both smooth and hazy regions of all InAsBi films observed but no atomic ordering is apparent using current imaging projections. Surface droplets present in hazy regions assume a zincblende crystalline structure that is usually tilted relative to the underlying dilute bismide film. Study of Bi-mediated InAs/InAs0.81Sb0.19 type-II superlattices indicates that the InAs-on-InAsSb interface still appears broadened relative to the InAsSb-on-InAs interface.