Interface sharpness in low-order III–V superlattices

• Published in: Thin solid films 1992-11, Vol.220 (1), p.176-183
• Main Authors: Pellegrino, J., Qadri, S.B., Amirtharaj, P.M., Nguyen, N.V., Comas, J.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/0040-6090(92)90569-W

Superlattices composed of aluminum, gallium and indium are currently employed in a variety of device-related applications. Among these are edge-emitting GRINSCH lasers and vertical cavity surface emitting laser diodes. As the individual layer thickness is reduced, the role of interface sharpness becomes more critical in ensuring good two-dimensional growth. This work addresses the relationship between interface roughness and superlattice crystallinity for short-period AlAs/GaAs superlattices. Thin short-period superlattices with active layer thicknesses of 30 nm or less were also investigated to help determine the interface sharpness in the initial stages of growth. X-ray diffraction was used to assess interface roughness and to calculate superlattice periodicity. These results are compared with those obtained by reflection high energy electron diffraction (RHEED), Raman spectroscopy, and spectroscopic ellipsometry. The results indicate that interface roughness is promoted by a reduced arsenic flux growth condition at normal growth temperatures for short-period superlattices. The results also suggest that, for thin superlattices, a 10 nm buffer layer enhances interface roughness in the initial stages of growth and compromises the subsequent epilayer crystallinity. An analysis of these results in the light of structural, dynamical, and optical data is presented.