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Interface Roughness-Induced Changes in the Near-E0 Spectroscopic Behavior of Short-Period AlAs/GaAs Superlattices

Published online by Cambridge University Press:  21 February 2011

D. Chandler-Horowitz ,
J.G. Pellegrino ,
N.V. Nguyen ,
P.M. Amirtharaj  and
S.B. Qadri
D. Chandler-Horowitz
Affiliation:
Semiconductor Electronics Division, NIST, Gaithersburg, MD 20899
J.G. Pellegrino
Affiliation:
Semiconductor Electronics Division, NIST, Gaithersburg, MD 20899
N.V. Nguyen
Affiliation:
Semiconductor Electronics Division, NIST, Gaithersburg, MD 20899
P.M. Amirtharaj
Affiliation:
Semiconductor Electronics Division, NIST, Gaithersburg, MD 20899
S.B. Qadri
Affiliation:
Condensed Matter Division NRL, Washington, DC 20375
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Abstract

The perturbations on the optical properties introduced by increased interface roughness in 3×3 short-period AlAs/GaAs superlattices (SL) were investigated through an examination of the position and line shape of the E0 (direct gap) feature in photoreflectance (PR) and spectroscopic ellipsometry (SE). The degree of interface roughness in the SLs was controlled by a choice of the growth conditions and the buffer layer thickness. The structural behavior was characterized by X-ray diffraction. The measured spectra from PR and SE were compared to those from an AlxGa,1-xAs (x≈0.5) alloy reference specimen grown under nearly identical conditions. The Гand E0values from the Al0 5Gao 5As alloy sample are valuable in this comparative analysis since they represent the lowest and highest bounds for the SL Гand E0, respectively. The results show that increasing interface roughness enlarges the linewidth, Г, from 42 meV to 64 meV, and the corresponding transition energy, E0, shifts from 2.060 eV to 2.112 eV; the reference values from the AlxGa,1-xAs (x≈0.5) sample are 26 meV and 2.137 eV, respectively. The upshift of E0 from the SLs with increasing interface roughness may be understood as a consequence of the roughening-induced intermixing and the eventual reduction in the modulation depth of the SL potential. The increase of Гalso with roughening suggests that additional mechanisms, such as roughening-induced scattering, are important.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 326: Symposium M – Growth, Processing, and Characterization of Semiconductor Heterostructures , 1993 , 145
Copyright
Copyright © Materials Research Society 1994

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