lecture: optical detection technologies for silicon photonics detectors.pdf · 1 lecture: optical...

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Lecture: Optical Detection Technologies for Silicon Photonics

Prepared by Laurent VIVIEN, Eric CASSAN, Delphine MARRIS-MORINI

Institut d’Electronique Fondamentale – UMR 8622CNRS - Université Paris Sud 11 – FRANCE

[email protected]://silicon-photonics.ief.u-psud.fr/

2Silicon Photonics –PhD course prepared within FP7-224312 Helios project

Micro- and nano-photonics:Which applications?

Integrated telecom transceiversHigher integration densityReduced component costs On-chip optical

interconnectsClock signal distributionHigh data rate links

(Optical network on chip)

New technology constraintsCompatibility with future CMOS TechnologiesElectronic / photonic integration

BiophotonicsStrong Light/matter interactionLow cost


Group IV materials

Transparent in 1.3-1.6 µm region

Take advantage of CMOS platform Mature technologyHigh production volume

Low cost and large SOI wafer available

High-index contrastSmall footprint, high EM field confinement

No electro-optic effect No detection in 1.3-1.6 µm region

High-index contrast for fibre coupling

Lacks efficient light emission

Silicon


High speed optical link

Laser:III-V on SiSi-based

Modulators:All Si

Passive structures:Waveguides,AWG,Couplers, …

Detectors:

TRANSMITTER

OPTICAL FIBER

RECEIVERTRANSMITTER

OPTICAL FIBEROPTICAL FIBER

RECEIVER


Basic principle

Photon absorption generate electron-hole pairsPhotogenerated carrier are then collected thanks to an external field

Photocurrent

e-

e-

h+

h+

hν

- +


Photodetector specifications (I)

Compatibility with silicon technologySilicon-based materials

Large wafer scale technology

Permit electronic integration (Transimpedance amplifier – TIA)

Low cost integration schemes

Broadband detection (1.3 -1.6 µm)

High absorption coefficient

Low dark currentDepend on the electrical configuration, the quality of the absorbing layer.


Photodetector specifications (II)

High bandwidth (frequency operation > 10 GHz)

Low carrier transit time,

Low RC constant – depend on the considered electrical structure (pin diode, MSM detector).

High responsivity Determine the configuration to achieve the best light interaction with absorbing layer.

Compactness

Strong absorption coefficient in the complete wavelength range


Outline

Absorption mechanisms: Material choiceBasics on photodetector characteristics

Quantum efficiencyResponsivityResponse timeDetector noise

Photodetector electrical structuresPIN diodes, MSM photodetector

Integration schemes of photodetectors and the states of the art


Absorption mechanisms (I)

If Ephoton < EgNo absorption

If Ephoton > EgDirect gap absorption

Inputphoton

gEh ≥ν.

E1

E2

e- energy

Conduction band:Sates in which electrons can move

Valence band:Non-conducting electron sates

Ev

Ec

GapEg

hole

electron

( )eVEµm

Ech

g

g

24,1)( <

<

λ

λ

Direct bandgap SC


Absorption mechanisms (II)

Direct gap SC

k

Ek

hν

k

Ek

hνPhonon

absorption

Phonon emission

Indirect gap SC

α

λ

λG

EG=hc/λG

α

λλG


Material choice

Two kinds of materials can be used:Direct gap SC: III-V materials Indirect gap SC: Group IV materials

Both have to be reported on the silicon platformIII-V SC bonded or epitaxial grown on silicon Group IV SC compatibles with silicon


Group IV materials

Silicon Germanium

Silicon GermaniumDirect bandgap > 3.4 eV (0.36µm) 0.80 eV (1.55µm)

Indirect bandgap 1.12 eV (1.10µm) 0.66 eV (1.88µm)

More suitable for visible absorption Absorption up to 1.55 µm


Material choiceWavelength ranges:

1.3 µm – 1.6 µm0.85 µm

Direct bandgap



1.3 µm – 1.6 µm0.85 µm

Indirect bandgap



1.3 µm – 1.65 µm0.85 µm

Indirect bandgap

Direct gap absorption


Material choice

In the 1.3 µm – 1.6 µm wavelength rangeInGaAs

• High absorption up to 1.7 µm

SiGe heterostructures ?

Bulk Ge?• High absorption up to 1.55 µm• Low Absorption from 1.55µm

Can Group IV materials strongly absorb lightat wavelengths up to 1.6 µm ?


Si1-xGex alloys

A transition occurs near a Ge mole fraction of about 14%:

• %Ge<85% ⇒ Si-like behavior

• %Ge>85% ⇒ Ge-like behavior

SiGe alloys with high Ge mole fractionsnecessary for light detection towards 1.55 µm

Si1-xGex

The absorption coefficient will be always lower than the one of bulk-Ge


Crystal lattice structure of Silicon and Germanium

Si and Ge have a diamond lattice structure (two interdigitated FCC lattices)

Properties Silicon GermaniumLattice parameter:

a (Å) 5.431 5.658

Atomic density (cm-3) 5,0.1022 4,42.1022

Atom radius (Å) 0.117 0,122Lattice structure Diamond Diamond

Lattice parameter mismatch: ~4.2 %


Germanium on silicon:Pros and Cons

Lattice misfit with Si of about 4.2%⇒ specific growth strategies required (wafer-scale and localized)

Low indirect bandgap: EG=0.66eV⇒ high dark current for MSM devices

Absorption coefficient of pure Ge:α≈9000 cm-1 at λ=1.3µm⇒ LABS

95% ≈ 3.3µm (!)⇒ Low capacitance devices⇒ High frequency operation

High carrier mobility

Can we directly growth Ge on silicon?


Ge growth strategies

Thick virtual SiGe substrates (10µm)Too thick for a good integration with optical waveguide

Growth on thin SiGe buffersThe thickness of the thin SiGe buffer is around 1µm

• Always too thick

Low/high temperature process


Germanium growth

Two-step growth process:Direct growth of Ge on Si using a low temperature ( ∼350°) CVD process⇒ thin (a few 10nm) highly-dislocated Ge layerGrowth of a thick Ge layer (a few 100nm) at a higher temperature ( ∼600°)⇒ high quality Ge absorbing layer

Thermal annealing to reduce the dislocation density

Si substrate (001)

LT Ge (∼350 C, ∼50nm)

HT Ge (∼600 C,∼300-500nm) ∼400nm


Absorption of Ge-on-Si

The red-shift of the absorption edge is due to the tensile strain-induced bandgap narrowing within the Ge layer, resulting from the difference in the thermal expansion coefficients of Ge and Si

Strong absorption up to 1.6µm


Epitaxial growth techniques

Molecular beam epitaxy (MBE)Solid sources evaporated ⇒ gas sputtering on the waferUltra-high vacuum required (P∼10-10 Torr)Low thermal budgets (T<∼550°C)High-control of layer and multi-layer thicknesses (<nm)Low growth rates (<1 nm/min)Some problems of uniformity for large areas and high-Ge mole fractions

Chemical Vapor Deposition (CVD):High-control of layer and multi-layer thicknesses (<nm)Proper for large wafer-scale fabricationA large variety of CVD techniques have been developed, depending on the pressure and heating systems:

• Ultra-High Vacuum CVD (UHV-CVD)• Reduced-pressure CVD (RP-CVD)• Low-energy plasma-enhanced CVD (LEPE-CVD)


Which material for which integration scheme?

The choice of the material for detection depends on the choice of the electronic / photonic integration.

What is the best materials for detectionin silicon platform?


1) Wafer bonding ofPIC (high T°C)

2) BE fab(<400°C)

Integration schemes

Combined front-end

fabrication

Photonic layer at the

last levels of metallizations with back-end

fabrication

Backside fabrication

•Through substrate connections•High integration density•Heterogeneous integration of III-V on Si

•Specific FE CMOS technology and library•Flip-Chip hybridization of InP components•Moderate integration density•Efficient connections of EIC and PIC

•Use of standard FE CMOS technologies•Heterogeneous integration of III-V on Si•High integration density (AboveIC)•Multilevel process capability

BE: Back end FE:Front end


2) BE fab(<400°C)



2) BE fab(<400°C)

Ge orInGaAs

InGaAs

Material choice versus integration scheme

Combined front-end

fabrication

Photonic layer at the

last levels of metallizations with back-end

fabrication

Backside fabrication

BE: Back end FE:Front end


2) BE fab(<400°C)

Ge orInGaAs

InGaAs

Ge


Outline






Photodetector characterisitics: Quantum efficiency (I)

Quantum efficiency (η):Probability of detecting an incident photon by generating an electron/hole pair that contributes to the photocurrent

Ratio of the generated carriers to incident flux of photons (i.e.: ratio of the photocurrent to the incident light power)

The spectral response is governed by the spectral character of the quantum efficiency


Quantum efficiency (η) depends on:Reflectance on the surfaceAbsorption

Photodetector characterisitics: Quantum efficiency (II)

L

α: absorption I0

0.IR

( )LRIIout .exp).1.(0 α−−=

( )[ ]LRIII outabs .exp1).1.(1 0 α−−−=−=The amount of flux that is absorbedin the material

( )[ ]LR .exp1).1( αη −−−=


Responsivity (ℜ) is often more useful to characterize the response of photodetectors

Responsivity is typically linear with wavelength but real photodetectors exhibit a deviation from the ideal behaviour due to photogenerated carrier trapping

Photodetector characterisitics: Responsivity

24.1)(.

.

. µmhq λη

υη

==ℜ


Response time of the photodetectors:Internal response timeExternal response time

Internal response timeTransit time of carriers: depends on the velocity of carriers in SC (varies with the doping level and the material)Diffusion time of carriers: diffusion of carrier to be collected. Mainly depends on the structure

Photodetector characterisitics: Response time (I)

t

Optical pulseResponse time


Photodetector characterisitics: Response time (II)

External response time

Cd Cp

Rd

R1

R2

Cd: Diode capacitance

Cp: Parasitic capacitance

Rd: Diode resistance

R1: contact and substrateresistances

R2: charge resistancetypical schematic electrical circuit of the photodiode

R1 and Rd << R2

Response time = R2 (CP + Cd)


Noise origin of photodetectors

Several noise sources:Quantique noise: constant noise due to the random character of electron-hole conversion

Shot noise: depends on the dark current and the photo-generated current

Thermal noise:

1/f noise• negligible for high speed photodiodes

fhP

fqiNS opts

∆=

∆=

..2.

..2/

2

νη

fR

kTiNS s

∆=

.4/

2

fiiNS

d

s

∆=

./

2

2

( )sdarkd iiqi += 22


Outline






MSM photodetectors: two schottky contacts

PIN diodes: P and N doped regions between undoped region

Photodetector electrical structures (I)

EF,P

CB

VB

-

+ VEF,N

P+ I N+

CB

VB

-

-

++

V

EFM

EFM

Metal MetalSemiConductor

Metal-Semiconductor-Metal PIN


Photodetector electrical structures (II)

MSM PIN

Surface contact MSM

380nmiD

iD

380 nm

Lateral contact MSM

P+ N+iD

380nm

Lateral PIN

N+i

3 µm

380nm

Vertical PIN

P+

M. Rouvière, PhD


Dark current

10-6

10-5

10-4

10-3

10-2

10-1

100

0 0,5 1 1,5 2 2,5 3

Lateral PINLateral contact MSMSurface contact MSMVertical PIN

Dar

k cu

rren

t (µA

/µm

)

Voltage (V)

No impact ionizationMSM: Schottky barrier height, PIN: thermal generation

Drift-diffusion 2D

Electrode spacing = 1µm

P+ N+

P+

N+

Idark ~ µA/µm

Idark ~ 10nA/µm

M. Rouvière, PhD

Example: Material: Ge


Dynamic capacitance

Drift-diffusion 2D

P+ N+

P+

N+

τRC = 50Ω*C

10-2

10-1

100

101

0 0,5 1 1,5 2 2,5 3

Vertical PINLateral PINLateral contact MSMSurface contact MSM

Cap

acita

nce

(fF/µ

m)

Voltage (V)

τRC ~ 18 fs

τRC ~ 500 fs

Ultra low capacitance

1V bias4µm photodetectors

M. Rouvière, PhD

Example: Material: Ge


Carrier collection time:Surface contact MSM photodetector

-1

0

1

2

3

4

5

6

0 10 20 30 40 50

Total currentHole currentElectron currentDisplacement current

Cur

rent

(µA

)

Time (ps)

Illumination by a short optical pulse (0.1ps)Carrier collection on the positive contact under 1V with D = 1µm

Drift-diffusion 3D

Response time: t = 14.2ps

t

Carrier evolution in MSM structure

Material: Ge

M. Rouvière, PhD


Carrier collection time: Surface contact MSM photodetector

Drift-diffusion 3DDrift-diffusion 2D

0

10

20

30

40

50

60

70

0 0,5 1 1,5 2 2,5 3

0.5µm1µm2µm

Col

lect

ion

time

(ps)

Voltage (V)

Electrode spacing:

2µm

1µm

0.5µm

Electric fields (1V)

Mode profile in accordance with electrode spacing

Material: Ge

M. Rouvière, PhD


Carrier collection times

0

5

10

15

20

0 0,5 1 1,5 2 2,5 3

Surface contact MSMLateral contact MSMLateral PINVertical PIN

Col

lect

ion

time

(ps)

Voltage (V)

Electrode spacing = 1µm

P+ N+

P+

N+

12.3ps (2V)

Response times:

9.7ps (1V)

9.5ps (1V)

4ps (0.5V)

Compatible with several 10GHz operation

Drift-diffusion 3D

M. Rouvière, PhD

Material: Ge


Outline




Integration schemes of photodetector and the states of the art


photodetector integration

Two choices

Surface illuminated photodetectors

photodetectors integratedin waveguide

High bandwidth“Simple” process

“Low” responsivity

High bandwidthHigh responsivity

Optical coupling

Detection at output fiber opticsfree space propagation

Detection in integrated photonics electronics circuits


Characterization methods:Responsivity

Surface illuminated diode

24.1)()/( µm

he

PIWAS q

q

ref

ph ληνη ===

PhotodetectorA

Ammeter Iph

WW Reference powerPref

.

Integrated diode

Photodetector

λ=1.3 or 1.5 µm

A

WW

Beam splitter

Chip edges

Optical fiber

WW Reference powerPref.

Non absorbed power

AmmeterIph

Input waveguide

Output waveguide

Reference waveguide

LPin.


S-parameter measurements

Characterization methods:Capacitance and resistances

Rs c

Cs c

Rs c

Cs c

CPW

(W,G,L)

RD U T

CDU T

Rs c

Cs c

Rs c

Cs c

CPW

(W,G,L)

RD U T

CDU T

S11 amplitude

S11 phase

Shortcut characteristics

Device undertest characteristics

Coplanar waveguide

RDUT and CDUT allow determining the RC constant


Characterization methods:Bandwidth (I)

Femtosecond pulse experiments

Opto-RF experiments with a Vector Network Analyzer


Characterization methods:Bandwidth (II)

Data transmission measurements

Eye diagram

Samplingoscilloscope

optical source

Bias T

Vpol

Optical fiber

RF cable

RF cable

optical modulatorλ = 1.55 µm

PRBSgenerator


Experimental set-ups

49Silicon Photonics –PhD course prepared within FP7-224312 Helios

project

Surface illuminated photodiodes

Interdigited MSM photodetectorsPIN diodes


Surface illuminated:MSM detector

Interdigited MSM photodetector

Ge thickness: 310nmElectrode spacing: 0.5 µm to 2 µmFinger width: 2µm

M. Rouviere et al., Appl. Phys. Lett. 87, 231109 (2005)

Electron lithographyMetal depositionLift-off


RF measurements (I)


0

0,2

0,4

0,6

0,8

1

0 40 80 120 160

Device under testAcquisition systemConvolution

Pho

tovo

ltage

(UA

)

Time (ps)

Response time under -2V bias: 5 ps

1/(2πτexp) = 32 GHz

-3dB bandwidth under -2V bias

35GHz

λ = 1.55 µm

Opto-RF experiments with a Vector Network Analyzer


RF measurements (II)


Opto-RF experiments

1/(2πτexp)

λ = 1.31 µm λ = 1.55 µm

λ = 1.55 µm

Bandwidth independent of the used method

Bandwidth independent of the wavelength


RF measurements (III)

The bandwidth is directly linked to the electrode spacing:Electrode spacing reduced by 2 ↔ Bandwidth increased by 2


Interdigited MSM photodetector

What are the main drawbacks of this kind of photodetector?

The dark current (few hundred of micro Amps)low Schottky barrierQuality of Ge grown on Si

The low responsivity due to the electrode shadow

What else?


PIN diodes

The thinner of i-Ge layer, the higher bandwidth, the lower responsivity


Fabrication surface illuminated PD

SOI substrate: √ BOX: 1µm; Si: 400 nm

P+-doped Si epitaxy (RPCVD) ~ 160 nm thick p+-Si

P+-doped Ge epitaxy at 400 C Undoped and N+-Ge epitaxy Mesa etching down to P+-Si Etching down to bottom contacts SiN deposit (PECVD) and AR coating SiN openings for electrode deposition Ti/TiN/AlCu metal stack

√ ~ 300 nm thick i-Ge√ ~ 150 nm thick N+-doped Ge film


Bottom contact

Top contact

Ge radius: 15 µmi-Ge thickness: ~300 nm

Ge N/Ge/Ge P

BOX

TiTiNAlCu SiO2/ SiN

N+

iP+

Top view Side view

Fabrication surface illuminated PD


Surface illuminated PD: Dark I-V

Photodetector diameter: 15 µm

3 µA dark current at -1V reverse bias

High dark current value due toabsence of thermal annealing

Mesa diameters


15µm diameter photodetector at 0 V bias.

Surface illuminated PD: responsivity

Responsivity under -1V:0.22 A/W for 25µm diameter

0.15 A/W at 1520 nm


Surface illuminated PD: Bandwidth measurements

Eye diagram at 40 Gb/s for a 10 µm diameter photodetector under 5 V reverse bias


Dark currentdensity at -1V

Responsivity(1550 nm)

Bandwidth(1550 nm)

Structure

Stüttgart

~0.1 A/cm²

~0.02 A/W

39 GHz

MIT Intel

~6 mA/cm²

~0.6 A/W(850 nm)

9 GHz(850 nm)

PIN

~10 mA/cm²

~.56 A/W

8.5 GHz

Singapore

15 GHz

~0.03 A/W

2005Year 20062005 2007

IEF & LETI

~1.5 A/cm²

~0.1 A/W

48 GHz

2009

~21 mA/cm²

PIN PIN PIN PIN

State of the art: surface illuminated photodetectors


project

Integrated photodiodes in silicon waveguide

MSM Ge photodetectorsPIN Ge diodes


Integrated photodetectors:optical coupling

Single mode (TE)

Rib SOI waveguides

Vertical coupling Butt coupling


Vertical coupling

BEP 3D

FDTD 3D

95 % absorption length < 10 µm with 310nm germanium thickness

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400 500 600

7 µm4 µm

10 µmAbs

orbe

d op

tical

pow

er

Germanium thickness (nm)

Length:

M. ROUVIÈRE, et al., Optical Engineering, 44 (2005) 183-187

0

0,2

0,4

0,6

0,8

1

0

20

40

60

80

100

0 2 4 6 8 10

Abs

orbe

d po

wer

(%)

Absorbed pow

er derivate (AU

)

Photodetector length (µm)

Absorption pow

er

SiGe


Butt coupling

95% absorption length < 4µm

Negligible lateral divergence


SOI substrate: BOX: 1µm; Si: 400 nm

Passive structures193nm deep UV lithographyRIE

Silicon recess down to 50 nmSelective Ge growth: RP-CVD

Dislocation density: 3.106 cm-3

SiO2 deposit (PECVD) and CMPSiO2 openings for electrode deposition

Ti/TiN/AlCu metal stack

√ 248 nm deep UV lithography√ RIE

√ 248 nm deep UV lithography, RIE

MSM


SiO2

SiSiO2

Si recess

GeSi waveguide

SiO2

SiO2

Integrated photodetectors: fabrication of MSM structure


Side view

Electrode spacings: 0.7 µm, 1 µm and 2 µm Ge length range: 6 µm to 25 µm Ge thickness: ~330 nm

Lwaveguide

RF electrodes

D

Top view

Integrated photodetectors: fabrication of MSM structure


Experimental results

Dark current mainly due to:Low Schottky barrierGe dislocationsMetal contacts

Responsivity~1 A/W at 1.55 µm and 1.31µm

⇒ 80% external efficiency


Bandwidth vs bias voltage

9.5 GHz

15 GHz

28 GHz

Electrode spacing: 1 µm


Measured photodetector response time

√ Convolution between Gaussian profile and a double exponential

Intrinsic response times:√ 35 ps at 1 V√ 28 ps at 2 V√ 19 ps at 6 V

-3dB bandwidths:√ 12 GHz at 1 V√ 16 GHz at 2 V√ 24 GHz at 6 V

Results:femtosecond pulse experiments


Bandwidth vs electrode spacing

Under 1V bias

4.2 GHz

9.5 GHz

17 GHz


Bandwidth vs wavelength

Response independent of the wavelength

Responsivity as high as 1 A/W at both wavelengths


Waveguide pin diode


Fabrication WG photodiode

SOI substrate: √ BOX: 1µm; Si: 400 nm

Passive structures Silicon recess down to 50 nm Ion Implantation (N+-doped Si ) Selective Ge growth: RP-CVD SiO2 deposit (PECVD) and CMP Bottom contacts down to doped Si SiO2 deposit (PECVD) SiO2 openings for electrode deposition

Ti/TiN/AlCu metal stack

√ 248 nm deep UV lithography√ RIE



√ ~ 300 nm thick i-Ge√ ~ 50 nm thick P+-doped Ge film

√248 nm deep UV lithography√RIE



Ge length: 15 µmi-Ge thickness: ~300 nm Ge width: 3 µm

InputWaveguide

ReferenceWaveguide

Bottom contact

Top contact

Bottom contact

Top contact

Ge 3 µm

Fabrication WG photodiode


~1 A/W at 1.55 µm under - 4V

Under -0.5 V:⇒ ~ 1 A/W at 1520 nm⇒ ~ 0.2 A/W at 1600 nm

Waveguide integrated PD: responsivity


Bandwidth measurements WG integrated

-3 dB bandwidth:12 GHz at 0 V~30 GHZ at -2 V> 40 GHz at -4 V12 GHz

28 GHz

42 GHz

- 3 dB

Data transmission:40 GBit/s at -4 V


Dark currentat -1V

Responsivity

Bandwidth

MSMStructure

IEF & LETI

~100 µA

~1 A/W

28 GHz

MIT INTEL

PIN

~170 nA

~0.9A/W

31 GHz

PIN

~1 µA

~1.08 A/W

7.2 GHz

Luxtera

PIN

~10 µA

20 GHz

~0.85 A/W

2007Year 20072007 2007

PIN

IEF & LETI

~20 nA

~1 A/W

42 GHz

2008

State of the art


project

III-V photodetector on silicon

MSM InGaAs photodetector


III-V photodetector on silicon

What are the possibilities to add III-V on silicon?

Same development for all III-V devices on silicon

Direct epitaxy using buffer layer

Molecular bondingof III-V wafer or dies

Manage to reduce the threading dislocations due to the lattice parameter mismatch


Die to wafer bonding: principle

CMOS

III-V


III-V on silicon for photodetection

Bonding layersSiO2/SiO2 molecular bondingBCB

Si wafer

Active III-V layers

Si

Accurate alignment of III-V with silicon waveguide is mandatory

Example of MSM III-V photodetector integrated in silicon waveguide


InGaAs/InAlAs photodetectors

2 coplanar Schottky contacts (Ti/Au)

InAlAs Schottky barrier enhancement layer (40nm)

InGaAs absorption layer (145nm)

InAlAs/InGaAs supperlattice (4x5nm)

(decrease carrier trapping at hetero-interface)

S

Si waveguide BCB

Ti/Au

i-InGaAs

S

Metal-semiconductor-metal detector with 2 coplanar Schottky contacts

BCB bonding layer (100nm)

SOI waveguide(same width as Schottky contact spacing)

(220nm deeply etched)

Side view

III-V MSM photodetectors


Simulation: optical coupling

Thin bonding layer = short couple length = efficient detection.200nm BCB bonding layer 90% of incident light is absorbed after 10μm.

L=30μm, d=400nm

IN

IN

InGaAs absorption

no absorption

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 5 10 15 20 25 30 35 40

Detector length (um)

Abs

orbe

d po

wer

frac

tion

(-)

200nm250nm300nm350nm


Fabrication

1. Sample preparation2. Sample cleaning + removal of cap layer3. BCB bonding and curing4. InP substrate removal5. Removal of sacrificial layers6. Detector mesa etching7. BCB insulation8. Opening of the contact windows9. Metallization10. Post-processing


DC characteristics3µm

Si waveguide

Ti/Au

i-InGaAs

3µm

BCB bonding layer

Experiments

QE = 80%

Idark = 3 nA (5V bias)Responsivity: 1 A/W at λ = 1550 nm -> QE ~80% under 5VSimulated bandwidth: 35GHz (1µm spacing, 5V bias)

1,E-10

1,E-09

1,E-08

1,E-07

1,E-06

1,E-05

1,E-04

0 2 4 6 8 10 12V(V)

I(A)

dark

12.8nW

126nW

1.26uW

12.4uW


State of the art

Dark currentat -1V

Responsivity

Bandwidth

PINstructure

UPS-IEF& LETI

~ 1 µA

~0.8 A/W

~ 90 GHz

MIT INTEL

PIN

~170 nA

~0.9 A/W

31 GHz

PIN

~1 µA

~1.08 A/W

7.2 GHz

INTEL

PIN

~50 nA

0.5 GHz

~0.31 A/W

EU- PICMOSproject

PIN

~1 nA

33 GHz

~0.45 A/W

2009Year 20072007 20072006

Ge-on-Si photodetectors III-V-on-Si photodetectors

IMEC

MSM

~1 nA

-

~1 A/W

2007-09

PIN

UPS-IEF& LETI

~ 20 nA

~ 1 A/W

42 GHz

2008

PIN

~1 nA

25 GHz

~0.7 A/W

2009

LUXTERA

PIN

~10 µA

~ 0.85 A/W

20 GHz

~ 2007

EU- PICMOSproject


Conclusion

Photodetection on silicon using either germanium or III-V materials is now a mature device10Gbit/s and 40 Gbit/s data transmission can be achieved for futur generation receivers

NOW!! What do we need to do?

Integration of TIA with photodetector


CMOS Photonics / Electronic integration:Ge photodiodes

Photonic wafer

Bonding on CMOS circuitBOX

Si substrate

Si film

waveguides

integratedphotodetectormodulator

Si substrate

BOX

Source of microelectronic circuit: IBM Processor on SOI (0.12µm)

Removal of the Si substrate

Silicon substrateSilicon substrate

Si substrate


Silicon rib waveguide

Germanium



Silicon rib waveguide

Ge cavity

Silicon

Metallisations

SiO2

No results on Photodetectors with TIA integration yet

For the next time!



Acknowledgements

IEF – Paris Sud University (Orsay, France)Mathieu ROUVIERESuzanne LAVALXavier LE ROUXPaul CROZATDaniel PASCALSamson EDMONDMathieu HALBWAX

French RMNT project (CAURICO)http://pages.ief.u-psud.fr/caurico/

IEF/MINERVECEA/LETI

Grenoble, France

Clean rooms

Basic Technological Research

European Community's Seventh Framework Program (FP7)

“pHotonics ELectronics functional Integration on CMOS”

CEA - LETI (Grenoble, France)Jean Marc FEDELIJean Michel HARTMANNJean François DALEMCOURT

Ghent University -IMEC (Belgium)Dries Van ThourhoutJoost BrouckaertWim BogaertsPieter DumonRoel Baets

lecture: optical detection technologies for silicon photonics detectors.pdf · 1 lecture: optical...

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