Optical Properties. Part 3

147 Pages·2007·2.951 MB·English

by  E. Kasper (auth.), E. Kasper, C. Klingshirn (eds.)

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Numerical Data and Functional Relationships
in Science and Technology
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Landolt-Börnstein
Numerical Data and Functional Relationships in Science and Technology
New Series / Editor in Chief: W. Martienssen
Group III: Condensed Matter
Volume 34
Semiconductor
Quantum Structures
Subvolume C
Optical Properties
Part 3
E. Kasper, N. Koshida, T.P. Pearsall, Y. Shiraki, G. Theodorou, N. Usami
Edited by E. Kasper and C. Klingshirn
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ISSN 1616-9549 (Condensed matter)
ISBN 978-3-540-47055-7 Springer Berlin Heidelberg New York
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ISBN 978-3-540-29647-8 Springer Berlin Heidelberg New York
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Editor in Chief: W. Martienssen
Vol. III/34C3: Editors: E. Kasper, C. Klingshirn
At head of title: Landolt-Börnstein. Added t.p.: Numerical data and functional relationships in science and technology.
Tables chiefly in English.
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I. Börnstein, R. (Richard), 1852-1913. II. Landolt, H. (Hans), 1831-1910.
III. Physikalisch-chemische Tabellen. IV. Title: Numerical data and functional relationships in science and technology.
QC61.23 502'.12 62-53136
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Editors
E. Kasper
Universität Stuttgart
Institut für Halbleitertechnik
70569 Stutttgart, Germany
email: [email protected]
C. Klingshirn
Universität Karlsruhe (TH)
Institut für Angewandte Physik
76131 Karlsruhe, Germany
e-mail: [email protected]
Authors
E. Kasper N. Koshida
Universität Stuttgart Tokio University of A&T
Institut für Halbleitertechnik Faculty of Electrical and Electronics
70569 Stutttgart, Germany Engineering
email: [email protected] Koganei, Tokyo 184-8588, Japan
email: [email protected]
T.P. Pearsall Y. Shiraki
18, Rue des Petits Champs Musashi Institute of Technology
75002 Paris, France Tokyo 158-0082, Japan
email: [email protected] email: [email protected]
G. Theodorou N. Usami
Aristotle University Tohoku University
Department of Physics Institute for Materials Research
Solid State Physics Section Sendai 980-8577, Japan
54123 Thessalonoki, Greece email: [email protected]
email: [email protected]
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Preface
The first two subvolumes III/34Cl and C2 on the Optical Properties of Semiconductor Quantum
Structures have been well received by the scientific community. They concentrated on theoretical
concepts (chapter 1), experimental methods (chapter 2), III-V semiconductors (chapter 4), I-VII
semiconductors (chapter 6), and IV-VI semiconductors (chapter 7) in subvolume Cl. The II-VII materials
(chapter 5) have been treated in subvolume C2.
The present subvolume III/34C3 finishes the review on optical properties, by adding the chapter 3 on
group IV materials.
There are exhaustive data on bulk materials including optical properties, starting from diamond C and
going over SiC, Si, Ge, to the semimetal grey Sn, and including their alloys—see e.g. Landolt-Börnstein,
New Series, Group III, Vol. 41Al(cid:302)1 and (cid:302)2, and A2(cid:302)1 and (cid:302)2.
Silicon is the backbone of the worldwide semiconductor industry. It is an indirect gap material, which
seriously hampers its use in light emitting or even laser diodes.
There are some ideas to overcome this problem by forming group IV quantum structures like Si/Ge
superlattices or nanocrystals. This hope triggers to a large extend the applied aspects of the research on
the optical properties of group IV quantum structures.
Though there are also relevant publications on the optical properties of group IV quantum structures
involving C or Sn, the by far largest part of work in this field is devoted to the system Si/Ge. Therefore
we concentrate here on this system.
The outline of this subvolume follows essentially the concept of the two preceding ones Cl and C2, but
with some differences in the details.
The first section 3.1 brings again some basic properties like the energy gaps or the effective masses and
proceeds then with in-depth information on the growth processes and the influence of the lattice misfit on
the growth techniques.
It is not possible in the Si/Ge system to circumvent this problem as it is in the ternary or quaternary
systems like AlGaAs, InGaAsP or ZnMgSSe, where the values of band gap and lattice constant can be
chosen within some limits independently. For this reason we bring in section 3.2 an overview of the
influence of strain on the band structures of Si and Ge and on the relative band line up between the two
materials, going in this field even more into depth in some of the following sections.
After these two introductory sections we start, similar as in the other subvolumes, in section 3.3 with
single, coupled, and multiple quantum wells. Section 3.4 is then devoted to the optical properties of
superlattices. Section 3.5 combines the data on quantum wires and on a special group of quantum dots,
namely those prepared by lithography of quantum wells, of selforganized quantum dots or –islands
occurring in a similar way as in various III-V and II-VI systems such as InAs/GaAs or CdSe/ZnSe.
Furthermore nanoclusters of e.g. Si in SiO are considered here. Nanoislands or localization sites
2
occurring usually in quantum wells due to thickness and/or composition fluctuations and with lateral
dimension which hardly result in quantization effects are only marginally treated in section 3.5.
A separate section 3.6 is devoted to porous or nanocrystalline Si. The observation of visible luminescence
from porous Si or Ge triggered a lot of research, caused again by the hope to obtain materials based on
these group IV semiconductors which allow the fabrication of efficient light emitting devices. During the
years of investigation it became obvious that not all light emission in these etched structures is due to Si
nanocrystals, but that there may be also contributions from siloxanes and similar Si O H compounds
x y z
formed during the etching process. Since the latter lead beyond the scope of this compilation, section 3.6
is devoted to results where the important role of Si nanocrystals is rather well established.
As in the two preceding subvolumes it is not the aim to cite and comment all work published so far on
optical properties of group IV quantum structures but to explain and to highlight prominent examples.
Some of the topics which are extensively studied in quantum structures of direct gap semiconductors such
as four wave mixing, lasing processes etc. are of minor importance for the group IV semiconductors.
Therefore the detailed structuring of this subvolume deviates in parts from the one of the chapters on e.g.
direct gap III-V, II-VI or I-VII quantum structures.
Acknowledgements
The editors thank all co-authors of this subvolume for the committed and careful preparation of their
manuscripts and the fruitful and stimulating cooperation during this book project. Thanks are due to Prof.
Dr. W. Martienssen, the editor in chief of Landolt-Börnstein, for his steady and demanding interest in the
progress of this work, and last but not least to Drs. R. Poerschke, W. Polzin and S. Scherer from Springer
for their patient, competent and extremely helpful support during the production on this book.
Stuttgart and Karlsruhe, January 2007 The Editors
Table of contents
Semiconductor Quantum Structures
Subvolume C3: Optical Properties (Part 3)
(edited by E. KASPER and C. KLINGSHIRN)
3 Group IV semiconductors 1
3.1 Basic properties, growth and preparation methods of group IV heterostructures
(by E. KASPER) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3.1.1 Epitaxial growth processes . . . . . . . . . . . . . . . . . . . . . . . 4
3.1.2 Lattice mismatch and its implication on critical thickness and interface structure . . . 13
3.1.3 Virtual substrates and strain relaxation. . . . . . . . . . . . . . . . . . . 17
3.1.4 References for 3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.2 Influence of strain on bandstructure (by E. KASPER) . . . . . . . . . . . . 19
3.2.1 Hydrostatic strain. . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2.2 Uniaxial strain. . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2.3 Band alignment of strained SiGe . . . . . . . . . . . . . . . . . . . . . 22
3.2.3.1 Average valence band energy E0 . . . . . . . . . . . . . . . . . . . . 22
v,av
3.2.3.2 Compressive strain . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.3.3 Tensile strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2.4 References for 3.2 . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3 Single and coupled quantum wells: SiGe (by N. USAMI and Y. SHIRAKI) . . . . . 26
3.3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.3.2 Photoluminescence from SiGe/Si quantum wells: Spectral features . . . . . . . . 27
3.3.3 Excitation power dependence of photoluminescence . . . . . . . . . . . . . 28
3.3.4 Temperature dependence of photoluminescence . . . . . . . . . . . . . . . 29
3.3.5 Quantum confinement effect . . . . . . . . . . . . . . . . . . . . . . 30
3.3.6 Effect of post-growth annealing . . . . . . . . . . . . . . . . . . . . . 31
3.3.7 Effect of electric field . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.3.8 Effect of external stress . . . . . . . . . . . . . . . . . . . . . . . . 33
3.3.9 Fermi-edge singularity. . . . . . . . . . . . . . . . . . . . . . . . . 34
3.3.10 Time-resolved photoluminescence . . . . . . . . . . . . . . . . . . . . 35
3.3.11 Growth mode transition . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3.12 Type-II strained Si quantum well. . . . . . . . . . . . . . . . . . . . . 38
3.3.13 Coupled quantum wells . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3.14 Electroluminescence . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.3.15 Interband absorption . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.3.16 Intraband absorption . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.3.17 Second-harmonic generation . . . . . . . . . . . . . . . . . . . . . . 44
3.3.18 Phonon modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.3.19 Cyclotron resonance . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.3.20 References for 3.3 . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Table of Contents ix
3.4 Optical properties of Si/Ge superlattices (by G. THEODOROU and E. KASPER) . . . 50
3.4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.4.2 The empirical tight-binding model . . . . . . . . . . . . . . . . . . . . 51
3.4.2.1 Uniaxial strain along the [001] direction . . . . . . . . . . . . . . . . . . 51
3.4.2.2 Uniaxial strain along the [111] direction . . . . . . . . . . . . . . . . . . 53
3.4.2.3 Optical properties. . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.4.3 Si/Ge SLs grown along the [001] direction . . . . . . . . . . . . . . . . . 53
3.4.3.1 Electronic properties . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.4.3.2 Optical properties. . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.4.3.3 Interface intermixing . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.4.4 Si/Ge SLs grown along the [111] direction . . . . . . . . . . . . . . . . . 61
3.4.5 Raman spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.4.5.1 Zone-folded acoustic phonons . . . . . . . . . . . . . . . . . . . . . . 64
3.4.5.2 Confined optical modes and interface modes . . . . . . . . . . . . . . . . 67
3.4.6 Photoluminescence (PL) . . . . . . . . . . . . . . . . . . . . . . . . 68
3.4.6.1 Effect of hydrostatic pressure on the PL . . . . . . . . . . . . . . . . . . 72
3.4.7 Electroluminescence (EL) . . . . . . . . . . . . . . . . . . . . . . . 74
3.4.8 Photoconductivity (PC) and optical Junction Space Charge Techniques (JSCT) . . . 74
3.4.8.1 Wannier-Stark localization . . . . . . . . . . . . . . . . . . . . . . . 77
3.4.9 Spectroscopic ellipsometry . . . . . . . . . . . . . . . . . . . . . . . 77
3.4.10 Piezoreflectance and electroreflectance . . . . . . . . . . . . . . . . . . 79
3.4.11 Second-harmonic generation . . . . . . . . . . . . . . . . . . . . . . 81
3.4.12 Quantum dot superlattices (QDSL) . . . . . . . . . . . . . . . . . . . . 82
3.4.13 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.4.14 References for 3.4 . . . . . . . . . . . . . . . . . . . . . . . . . . 86
3.5 Si, Ge, and SiGe quantum wires and quantum dots (by T.P. PEARSALL) . . . . . 89
3.5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.5.2 Silicon and germanium quantum-wire quantum-dot structures . . . . . . . . . . 92
3.5.3 Synthesis of quantum wires and quantum dots. . . . . . . . . . . . . . . . 94
3.5.3.1 Self-organized epitaxy of quantum dots . . . . . . . . . . . . . . . . . . 94
3.5.3.2 Lithographic definition of quantum structures . . . . . . . . . . . . . . . . 99
3.5.3.3 Synthesis of free-standing Si quantum dots . . . . . . . . . . . . . . . . . 101
3.5.3.4 Photoluminescence properties of Si nanoclusters . . . . . . . . . . . . . . . 103
3.5.3.5 Si quantum dots formed by controlled segregation of excess Si in SiO . . . . . . 103
2
3.5.3.6 Si quantum dots formed by the controlled segregation of excess Si in SiN . . . . . 107
x
3.5.4 Applications of SiGe quantum-dot structures . . . . . . . . . . . . . . . . 108
3.5.4.1 SiGe quantum-dot photodetectors . . . . . . . . . . . . . . . . . . . . 108
3.5.4.2 Si quantum-dot light-emitting diodes . . . . . . . . . . . . . . . . . . . 111
3.5.4.3 Er-doped Si-SiO nanocluster optical amplification . . . . . . . . . . . . . . 114
2
3.5.4.4 Si quantum-dot memories . . . . . . . . . . . . . . . . . . . . . . . 115
3.5.5 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
3.5.6 References for 3.5 . . . . . . . . . . . . . . . . . . . . . . . . . . 118
3.6 Luminescence and related properties of nanocrystalline porous silicon
(by N. KOSHIDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
3.6.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
3.6.2 An overview of nanostructured silicon. . . . . . . . . . . . . . . . . . . 121
3.6.3 Fabrication technology. . . . . . . . . . . . . . . . . . . . . . . . . 122
3.6.3.1 Nanocrystalline porous silicon. . . . . . . . . . . . . . . . . . . . . . 122
3.6.3.2 Dry-processed silicon nanocrystallites . . . . . . . . . . . . . . . . . . . 123