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Photoreflectance Study of Modulation-Doped GaAs/GaAlAs Quantum Dots Fabricated by Reactive-Ion Etching

Published online by Cambridge University Press:  22 February 2011

P.D. Wang ,
C.M. Sotomayor Torres ,
M.C. Holland ,
H. Qiang ,
F.H. Pollak  and
G. Gumbs
P.D. Wang
Affiliation:
Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow, G12-8QQ, Scotland
C.M. Sotomayor Torres
Affiliation:
Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow, G12-8QQ, Scotland Royal Society of Edinburgh Research Fellow
M.C. Holland
Affiliation:
Department of Electronics and Electrical Engineering, University of Glasgow, Glasgow, G12-8QQ, Scotland
H. Qiang
Affiliation:
Physics Dept., Brooklyn College of CUNY, Brooklyn, NY, 11210, USA
F.H. Pollak
Affiliation:
Physics Dept., Brooklyn College of CUNY, Brooklyn, NY, 11210, USA
G. Gumbs
Affiliation:
Physics Dept., Hunter College of CUNY, New York, NY, 10021, USA
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Abstract

Using contactless photoreflectance at 300K and 77K we have investigated the intersubband transitions from two modulation-doped GaAs/GaAlAs quantum dot (QD) arrays fabricated by reactive-ion etching (RIE). The samples consisted of 8 nm decoupled GaAs/GaAlAs quantum wells with dot sizes (lateral dimensions) of 60 and 100 nm. The lineshapes of the “IC-IH” and “IC-IL” features were indicative of a screened exciton, i.e., the derivative of a broadened twodimensional density of states (step function), due to the presence of the electron gas. On the other hand, even at 300K the “2C-2H“ features exhibited a well-defined sharp excitonic lineshape, i.e., derivative of a Gaussian profile. Even at room temperature it is possible to detect the effects of the lateral quantum confinement. We have observed a 2 meV blue shift of the “2C-2H” feature of the 60 nm QD array in relation to the 100 nm QD array. At 77K we have found evidence for a “parabolic-like” in-plane confining potential on the smaller QD array. This experiment demonstrates the considerable utility of PR in studying these reduced dimensional systems.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 324: Symposium K – Diagnostic Techniques for Semiconductor Materials Processing , 1993 , 187
Copyright
Copyright © Materials Research Society 1994

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