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Quantum Confinement of Above-Band-Gap Transitions in Ge Quantum Dots

Published online by Cambridge University Press:  10 February 2011

C. W. Teng ,
J. F. Muth ,
R. M. Kolbas ,
K. M. Hassan ,
A. K. Sharma ,
A. Kvit  and
J. Narayan
C. W. Teng
Affiliation:
Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695–7911
J. F. Muth
Affiliation:
Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695–7911
R. M. Kolbas
Affiliation:
Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27695–7911
K. M. Hassan
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7907
A. K. Sharma
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7907
A. Kvit
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7907
J. Narayan
Affiliation:
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695–7907
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Abstract

A number of research efforts have been focused on self-assembled germanium quantum dots in which indirect optical transitions take place across the band gap. However, many questions regarding the confined electronic state transitions of Ge quantum dots still remain unanswered. In the present report, we have deposited ten alternating layers of crystalline Ge quantum dots embedded in an Al2O3 or an AIN matrix on sapphire substrates by pulsed laser deposition. The average dot sizes (73 Å to 260 Å) were controlled by the laser energy density, deposition time and substrate temperature. The spectral positions of both the E1 and the E2 transitions in the absorption spectra at room temperature and 77 K shift toward higher energy (ΔE1=1.19 eV, ΔE2 =0.57 eV) as the Ge dot size decreases (73 Å). Structural analysis using transmission electron microscopy and atomic force microscopy and the interpretation of optical absorption measurements in terms of quantum confinement of carriers in both transitions are presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 588: Symposium P – Optical Microstructural Characterization of Semiconductors , 1999 , 263
Copyright
Copyright © Materials Research Society 2000

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