Intermixing and lateral composition modulation in GaAs/GaSb short period superlattices

Abstract

Lateral composition modulation on the group V sublattice has been investigated in GaAs/GaSb short period superlattices. The effect of As species and growth temperature on the appearance of lateral composition modulation was studied. Cross-sectional transmission electron microscopy and x-ray diffraction reciprocal space maps reveal that structures grown using As tetramers are always disordered, defective, and phase separated. Also, in these structures the As-rich regions appear to be composed of stacked GaAs quantum dots embedded in a GaSb matrix. The structures grown with As dimers show improved crystalline quality. Short period superlattices grown at T<420 °C have flat interfaces and are laterally homogeneous, however, there is significant anion intermixing across the interfaces. Structures deposited at 420 °C<T<445 °C roughen during growth, and exhibit lateral composition modulation and anion intermixing. Growing at higher temperatures destroys both the superlattice structure and the lateral composition modulation. The As sticking coefficient was calculated and was found to range between 0.1⩽σ⩽0.17 depending on the growth temperature and As species.