Le Nanotecnologie per una Fotonica
a base di Silicio
Francesco Priolo
MATIS-INFM & University of Catania
Napoli, 10 Marzo 2005
Moore’
s Law
More than Moore
Si Optoelectronics MEMS
Biochips
Molecular
Power
generation devices
More Moore
diversification
130nm
90nm
65nm
BiCMOS
Optical data
communicationrf CMOS
+ passives
Diagnostic
devices
embedded
MEMS
45nm
Environment
conscious devices
Advanced
smart devices
data storage
32nm
miniaturization
Moore’
s law
Nanotechnologies plays a major role in both cases!!
dedicated
Novel
markets
Interconnect length per chip versus year
Interconnect bottleneck
Motivations
• The obvious choice towards the solution of the
interconnect bottleneck would be to have silicon based,
VLSI compatible, optical interconnects
• The major limitations towards this dream is the absence
of an efficient Si-based light source
Optical chip
Milestones in Si Photonics
1990
Room Temperature Light Emission by Quatum
Confinement Effects (Porous Si)
1994
First Electroluminescent Si Device emitting at 1.54
micron at room temperature (Erbium in Si)
2000
Optical Gain from Si nanocrystals is discovered
2005
The first All-Silicon Laser (by Raman stimulated
emission) is demonstrated
Missing: An electrically pumped laser
Si nanocrystals
nanocrystals
Si
Quantum confinement
4.0
Energy gap (eV)
3.5
1.1 eV
3.0
2.5
2.0
1.5
1 nm
0.5
1.0
1.5
2.0
Crystal radius (nm)
2.5
Silicon Nanocrystals
Room temperature Si nc luminescence spectra
1250 °C 1 h
1,2
PL Intensity (a.u.)
Si nc radius
1,0
35 at. Si
37 at. Si
39 at. Si
42 at. Si
44 at. Si
0,8
0,6
0,4
0,2
0,0
600 700 800 900 1000 1100 1200
Wavelength (nm)
TEM and SEM images of a Si nc device
Metallization
Poly-Si
x
SiO x
Si substrate
100 nm
20 m
EMMI image of a light emitting Si-nc device
Erbium-Doped
Erbium-Doped
Si nanocrystals
nanocrystals
Si
Er3+ energy levels
Loss (dB/km)
100
50
Silica optical fiber
10
5
1.3 m
0.6 dB/km
0.9 m
1.5 dB/km
1.55 m
0.2 dB/km
1
.5
.1
.7
.8
.9
1.0
1.1
1.2
1.3
Wavelength (m)
1.4
1.5
1.6
1.7
Light transport
BIT 1
Optical fiber
BIT 0
Optical
amplifiers
Room temperature photoluminescence
3.0
Er doped Si nanocrystals
Er doped SiO2
PL Intensity (a.u.)
2.5
2.0
1.5
4I
11/2
4I
13/2
1.54 m
10 mW
4I
1.0
15/2
x5
0.5
0.0
1400
1500
1600
Wavelength (nm)
1700
0.8 m
Er3+
Si nc
Si nc
0.8 m
1.54 m
Light Emitting MOS
Al
0.2 m
Al
c-Si
0.5 m
Poly-Si
SiO2+nc+Er
c-Si
Poly-Si
SiO2+nc+Er
c-Si
SiO2
0.2 m
c-Si
SiO2
Poly-Si
SiO2+nc+Er
Electroluminescent MOS device
400
EL Intensity (arb. units)
SEM
14
2
7x10 Er/cm
350
2
20 A/cm
300
250
200
150
100
50
0
1.4
0.3 mm
1.5
1.6
Wavelength (m)
1.7
Er and Si nanocluster optical amplifier
1.54 m
Er3+
Stimulated emission
Si nc
Er3+
photon
The colorful world of rare earth doped Si nc
1.2
Normalized PL Intensity
Nd
1.0
Er
Er
Si nc
Tm
0.8
0.6
Yb
Tm
0.4
0.2
0.0
600
800
1000
1400
Wavelength (nm)
1600
1800
Photonic crystals
crystals
Photonic
What is a Photonic Crystal?
It is an optical material…
…periodically patterned/microstructured…
…on the scale of the wavelength of light
Crystals -> for their periodicity
Photonic -> because they act on light
Artificial 3D Photonic Crystals
The woodpile crystal is a fcc
crystal initially proposed by a
group at Iowa State University.
It can have a complete photonic
band gap and is widely studied.
woodpile crystal
1 m
2D Photonic Crystals: planar waveguides
Light emitting MOS devices with a surface
photonic crystal structure
Cristallo fotonico bidimensionale
Polysilicon
Si nc and Er
Si substrate
L’
efficienza di estrazione della luce è aumentata dalla presenza del cristallo fotonico.
Photonic crystals can be found in Nature
Butterfly wings
Bar=1m
SEM images
H. Ghirandella
Appl. Opt. 30 p.3492
1991
Conclusions
Si nanocrystals have powerful
pontentials in optoelectronics
20 nm
Efficient electroluminescent devices have
been fabricated
Erbium doped Silicon nanoclusters might represent a suitable
system for the fabrication of
electrically driven optical amplifiers
Photonic crystals represent a powerful tool to
control light propagation and efficiently extract light