Reviewing SiC photo-sensing devices

Manuela Vieira Manuel Vieira Paula Louro Miguel Fernandes Alessandro Fantoni João Costa Victor Silva Manuel Barata

Lisbon 1

The Eighth International Conference on Sensor Device Technologies and Applications SENSORDEVICES 2017

September 10 - 14, 2017 - Rome, Italy

NOBEL in Physics 2009

TWO REVOLUTIONARY OPTICAL TECHNOLOGIES

“The Nobel Prize in Physics 2009 honors three scientists, who have played important roles in shaping the modern information technology, with one half to Charles K. Kao and with Willard S. Boyle and George E. Smith sharing the other half.”

Charles K. Kao Willard S. Boyle

George E. Smith

1. W.S. Boyle and G.E. Smith, Bell Systems Technical Journal 49 (1970) 587; G.F. Amelio, M.F. Tompsett and G.E. Smith, ibid. 49 (1970) 593. 2. J.R. Janesick: Scientific Charge-Coupled Devices (SPIE Press, 2001).

1. J. Hecht, “City of light. The story of fiber optics”, Oxford University Press (1999). 2. K.C. Kao and G.A. Hockham, “Dielectric-Fibre Surface Waveguides for optical frequencies” Proc. IEEE, 113, 1151 (1966).

Useful reading

Apparently the first still remaining photograph was produced by J.N. Niépce in 1826 using a camera obscura with an 8 hour exposure time.

W.H.F. Talbot invented in 1841, light sensitive papers containing silver salts for first obtaining a negative image and there after, through contact copying with another light sensitive paper, a positive image. In 1888 the Eastman Kodak box camera for roll film appeared on the market.

Charge-Coupled Devices

G. Lippman was awarded the 1908 Nobel Prize in Physics for his color photographic process based on interference effects. Traditional color films consist of three light sensitive emulsions with different sensitivities for light: top layer for blue, middle layer for green, and bottom layer for red. Film capture full color at every point in the image.

Kodak developed the Bayer filter mosaic pattern used for CCD image sensors (1975), only after the groundbreaking CCD invention (1970) W.S. Boyle and G.E. Smith.

The CCD digital image sensors were only capable of recording just one color at each point in the captured image instead of the full range of colors at each location.

Full color image sensors

p+hg

Ec

E v

w

i n+i n+

Pinc

Pinc

JdlJdif

Jdif

Jdl

++

+

--

-

p+hg

Ec

E v

w

i n+i n+

Pinc

Pinc

JdlJdif

Jdif

Jdl

++

+

--

-

p+hg

Ec

E v

Ec

E v

w

i n+i n+

Pinc

Pinc

JdlJdif

Jdif

Jdl

++

+

--

-

All of these devices use essentially the same light sensing mechanism. Photons penetrating a depletion region generate electron-hole pairs. These carriers are swept away by the electric field across the depletion region and generate a small transverse photocurrent.

p_-Si

Clock

Potential well

SiO2

+V -V

One color at each point in the captured image

Full range of colors at each location

#1 #2a #2b

Device Architecture

•Produced by PECVD •The thickness of the front photodiode are optimized for blue collection and red transmittance •The thickness of the back photodiode was adjusted to achieve high collection in the red spectral range

ITO

G

lass

p

i’(a-S

iC:H

)

i (a

-Si:H

)

n

p

n

ITO

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,410

24

1x1025

1x1026

400 nm 580 nm

450 nm 615 nm

470 nm 650 nm

550 nm

Genera

tion (

m-3s

-1)

Position (m)

Both front and back diodes act as optical filters confining, respectively, the blue and the red optical carriers, while the green ones are absorbed across both.

Fro

nt

Back

Light-to-dark sensitivity (Homo- vs Hetero-structures)

400 450 500 550 600 650 700 750 8000,0

0,2

0,4

0,6

0,8

1,0

L=2 mWcm

-2

L=1 mWcm

-2

L=0#M007192

RN

Wavelenghth (nm)

400 450 500 550 600 650 700 750 8000,0

0,2

0,4

0,6

0,8

1,0

L=2 mWcm

-2

L=1 mWcm

-2

L=0#M007192

RN

Wavelenghth (nm)

400 450 500 550 600 650 700 750 8000,0

0,2

0,4

0,6

0,8

1,0

L=4 mWcm

-2

L=0

#M006291

RN

Wavelength (nm)

400 450 500 550 600 650 700 750 8000,0

0,2

0,4

0,6

0,8

1,0

L=4 mWcm

-2

L=0

#M006291

RN

Wavelength (nm)

Homostructure: • light bias independent • no light-to-dark sensitivity

Heterostructure

•light bias dependent.

• light-to-dark sensitivity

GlassITO

P

i-Si:H (1000 nm)

nITO

GlassITO

P

i-Si:H (1000 nm)

nITO

s d D E s d / s ph

Single

films ( W-1 cm -1 ) (eV)

p-Si:H 8.2 10 -7 0.499 7.3

p-SiC:H 2.5 10 -9 0.649 4.5

i-Si:H 7.6 10 -11 0.739 7.1 10

4

n-Si:H 7.8 10 -7 0.426 1.2

n-SiC:H 1.9 10 -12 0.834 21

GlassITO

P

i-Si:H (1000 nm)

nITO

GlassITO

P

i-Si:H (1000 nm)

nITO

Light-to-dark sensitivity

400 450 500 550 600 650 700 750 8000.00

0.05

0.10

0.15

0.20

#1(L=0)

#1b(L=0)

#1a(L=0)

Sen

siti

vit

y (

A/W

)

Wavelength (nm)

0,0 1,0 2,0 3,0 4,0 5,0 6,0

i ac

(L)/

i ac(0

)

L (mWcm

-2)

0,0

0,2

0,4

0,6

0,8

1,0

#1a

#1

#1b

#1 (2mWcm-2

)

#1a(2mWcm-2)

#1b(2mWcm-2)

The light-to-dark ratio depends strongly on the carbon concentration of the doped layers.

p

i

n

a-SiC:H a-Si:H

When highly resistive a-SiC:H doped layers are used its higher optical gap when compared with the active layer are responsible by charge accumulation at the illuminated interfaces which blocks the carrier collection under illumination. Those insulator-like layers prevent excess signal charge from blooming to the nearby dark regions avoiding the image smearing.

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,10,2

0,30,4

0,50,6

0,00,2

0,40,6

0,81,0

Pote

ntial (V

)

Position (m)

Voltage (V

)

-0,6

-0,4

-0,2

0,0

0,2

0,4

0,6

0,10,2

0,30,4

0,50,6

0,00,2

0,40,6

0,81,0

Pote

ntial (V

)

Position (m)

Voltage (V

)

p

n

p

i

n

Scanner

i p

i

n

0 10 20 30 40 50 600,0

0,5

1,0

1,5

2,0

2,5

3,0

Dark DarkIlluminated

Bias (V)

i ac (

nA

)

Position (a.u)

Laser Scanned Photodiode Technique

Imagem

iac

• The LSP utilizes light modulated depletion layers as detector and a laser beam for readout.

Heterostructure

•light-to-dark sensitivity

M. Vieira, M. Fernandes, J. Martins, P. Louro, R. Schwarz, and M. Schubert, “Laser Scanned p-i-n Photodiode (LSP) for image detection” IEEE Sensor Journal, 1, no.2 pp. 158-167

ITO p

i

n ITO

Laser Scanned Photodiode Image Sensor (LSP)

Matrix intensity

Xm,n =-(Im,n- Sm,n)

Glass

A large cell detector where the image is scanned by sequentially detecting scene information at discrete XY coordinates.

p(a-SiC:H)/i(a-Si:H)/n(a-SiC:H)

Characteristics

•No pixels •p-i-n structure and two contacts •Integrated read-write system. •In time image processing.

p-i-n p-i-n

Laser Scanned Photodiode Color Sensor (CLSP)

•p-i-n B&W LSP image sensors were produced and tested.

•The tandem structure takes advantage on the radiation wavelength selectivity due to the different light penetration depth inside the a-Si:H and a-SiC:H

Large area color image sensors with improved response.

M. Vieira, P. Louro, M. Fernandes, and A. Fantoni “Optical confinement in a Double Colour Laser Scanned Photodiode (D/CLSP)” Sensor and Actuators A 114/2-3 (2004), pp. 219-223

400 500 600 700 800

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35Front cell

ITO/pi´(a-SiC:H)n/ITO/pi(a-Si:H)n/ITO

Ph

oto

cu

rre

nt

(a

)

Wavelength (nm)

0.0

0.5

1.0

1.5

2.0-5V

+1V

-10 -8 -6 -4 -2 0 20.0

0.1

0.2

0.3

0.4

0.5

Photo

curr

ent (

A)

Front cell

ITO/pi´(a-SiC:H)n/ITO/pi(a-Si:H)n/ITO

Photo

curr

ent (

A)

Voltage (V)

650 nm

550 nm

450 nm

600 nm

500 nm

-1.2

-0.8

-0.4

0.0

0.4

Back cell

Optical filter

Front diode –Cuts the red

Back diode –Cuts the blue

Back cell

400 500 600 700 800

0.0

0.1

0.2

0.3 NC10 p-i'(a-SiC:H)-n-p-i(a-Si:H)-n

75 Hz

Ph

oto

cu

rre

nt

(A

)

Wavelength (nm)

-10 V

-5 V

0 V

+3 V

Spectral response

Voltage controlled spectral response.

•As the applied voltage changes from forward to reverse the blue/green spectral collection is enlarged while the red one remains constant

Full colour recognition

450 500 550 600 650

Front diode

Optical image

a-SiC:H

a-Si:H

V1

V2

Electronic image

V=V1+V2

02

2,2

)(ln

I

IVIVV Tlight

02

02,2

)(ln

I

IVIVV Tdark

02

2,2 ln

I

IVIVV Tlight

02

02,2 ln

I

IVIVV Tdark •Color rejection

•Image recognition

0201

21lnII

IIIIVV T

CLSP take advantage of the fact that red, green, and blue light penetrate silicon to different depths forming an image sensor that captures full color at every point in the captured image without the need of pixels.

-0.5

0.0

0.5

1.0

1.5

5

10

15

2025

3035

40

510

1520

25

Ph

oto

cu

rren

t (m

A)

X position

Y positi

on

-6V

-6 -5 -4 -3 -2 -1 0 1 2

-8x10-8

-6x10-8

-4x10-8

-2x10-8

0

b)

a)

S=650 nm

NC#5 (pin/pin)

whithout

optical bias

L=550 nm

L=650 nm

L=450 nm

Photo

curr

ent (A

)

Voltage (V)

Color recognition

Self reverse bias effect

M. Vieira, M. Fernandes, P. Louro, C. Mendes, R. Schwarz, Y. Vigranenko “OSIP Optical signal and image processing device optimized for optical read-out” Sensor and Actuators A: Physical, 120 (2005) pp. 88-93

55

55

55

400 450 500 550 600 650 700 750 8000,0

0,2

0,3

0,5

0,7

0,8

1,0

L=0.1 mWcm

-2

L=0

Heterostructure

p-i-n-p-i-n

RN

Wavelength (nm)

Optical amplification

0.0 1.0 2.0 3.0 4.0 5.00.0

0.5

1.0

1.5

2.0

2.5

3.0Red channel

Ph

oto

cu

rre

nt (a

.u.)

Time (ms)

V=-8V

no bias,

L=650 nm

L=470 nm

L=470 nm

V=+1V

no bias

L=650 nm

L=524 nm

L=470 nm

0.0 1.0 2.0 3.0 4.0 5.00.0

0.5

1.0

1.5

2.0

2.5

3.0

V=+1V

no bias

L=650 nm

L=524 nm

L=470 nm

V=-8V

no bias,

L=650 nm

L=470 nm

L=470 nm

Green channel P

ho

tocu

rren

t (a

.u.)

Time (ms)

B

C

D

E

F

G

H

I

0.0 1.0 2.0 3.0 4.0 5.00.0

0.5

1.0

1.5

2.0

2.5

3.0

V=+1VV=-8V

no bias

L=650 nm

L=524 nm

L=470 nm

no bias,

L=650 nm

L=470 nm

L=470 nm

Blue channel

Ph

oto

cu

rre

nt (a

.u.)

Time (ms)

B

C

D

E

F

G

H

I

ITO

Gla

ss p

i’(a-S

iC:H

)

i (a

-Si:H

)

n p nIT

O

ITO

Gla

ss p

i’(a-S

iC:H

)

i (a

-Si:H

)

n p nIT

O

Self reverse bias effect

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6-4x10

5

-3x105

-2x105

-1x105

0

1x105

-6V

+2V

NC#5

L=650 nm

Ele

ctr

ical field

(V

/m)

Position (m)

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6

-2,0x105

-1,5x105

-1,0x105

-5,0x104

0,0

5,0x104

1,0x105

L=550 nm

+2V

-6V

NC#5

Ele

ctr

ical field

(V

/m)

Position (m)

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4

-2,0x105

-1,5x105

-1,0x105

-5,0x104

0,0

5,0x104

1,0x105

+2V

-6 V

NC#5

L=450 nm

Ele

ctr

ical field

(V

/m)

Position (m)

When an external electrical bias is applied, it mainly influences the field distribution within the less photo excited sub-cell.

Blue bias amplifies the red and the green channels and reduces the blue. Red bias reduces the red and green channels and amplifies de blue. Green bias reduces the green channel keeping the others almost constant.

Front

diode

Back

diode

-

Substrate InOx

p (a-SiC:H)

n (a-SiC:H)

i (a-SiC:H)

200 nm

p (a-SiC:H)

i (a-Si:H)

1000 nm

n (a-SiC:H)

n (a-SiC:H) InOx

B R G

B

R

G

V

Wavelength Division Multiplexing

Wavelength Division Demultiplexing

•The tandem structure takes advantage of the radiation wavelength selectivity due to the different light penetration depth inside the a-Si:H and a-SiC:H

Divison Wavelength Multiplexing Device (WDM)

M. Vieira, P. Louro, M. Fernandes, M.A. Vieira, A. Fantoni and M. Barata, “Large area a-SiC:H WDM devices for signal multiplexing and demultiplexing in the visible spectrum”, Thin Solid Films 517 (2009), pp. 6435-6439. DOI:10.1016/j.tsf.2009.02.096

Bias sensitive WDM device

V

0.0 1.0 2.0 3.0 4.0 5.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

V=+1V

V=-8V

G

BR

B (-8V)

R(-8V)

G(-8)

B(+1)

R(+1)

G(+1)

Led R

Led G

Led B

Ph

oto

cu

rre

nt (

A)

Time (ms)

R+G+B R&G&B

soma

+1V

-8V

###

###

###

###

###

###

###

###

###

Optical amplification under negative bias. !!!!!

•High: all the channels ON •Low: all the channels OFF. •The signal due to the mixture of two input channels (R&B, R&G, G&B) are higher than only one (R, G, B).

Under negative applied voltages, the multiplexed signal keeps the memory of the single input channels.

0.0 1.0 2.0 3.0 4.0 5.00.0

0.2

0.4

0.6

0.8

Photo

curr

ent(

A

)

Time (ms)

0.0 1.0 2.0 3.0 4.0 5.00.0

0.2

0.4

0.6

0.8

Time (ms)

0,0 1,0 2,0 3,0 4,0 5,00,0

0,2

0,4

0,6

0,8

1,0

1,2

&0

&B

&B

0&

0

B

R&G

R&G G

GR R

0&0 R / GR / GR&G

t=Tt=0

00110011

01010010

00111100

V=+1

V=-8V

Green

Blue

Red

E

F

B

C

D

Photo

curr

ent(uA

)

Time (ms)

R&G

R&G R

/G

R/G

G/R

G/R

0/B

0/B

R&G

R&G R

/G

R/G

G/R

G/R

0/B

0/B

X

X X X X X

B

B

0&0&0

WDM – Recovery of the input channels

Using this simple algorithm the independent red, green and blue bit sequences can be decoded as: R[00111100], G[00110011] and B[01010010].

ELECTRICAL MODEL

I2

15u

I

I II

C2

1000p

I

0

Q1 V

Q2

I

I1

15u

C1

2500p

I3

10u

I4

8u

I

I2

15u

I

I II

C2

1000p

I

0

Q1 V

Q2

I

I1

15u

C1

2500p

I3

10u

I4

8u

I

Negatively biased The p-n internal junction is forward-biased

Positively biased The p-n internal junction is reverse-biased

M A Vieira, M. Vieira, M. Fernandes, A. Fantoni, P. Louro, M. Barata, Amorphous and Polycrystalline Thin-Film Silicon Science and Technology — 2009, MRS Proceedings Volume 1153, A08-03

Q1

Q2 i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

p

i

n

p

p

i

n

p

p

i

n

p

p

i ’

n

p

p

i

n

p

p

i

n

p

p

i

n

p

p

i

n

p

p

i ’

n

p

I1

I2

I3

I4

0 1 2 3 4-20

-10

0

10

20

30

I(C2)

I(C1)

I4

I2

I(+1)

I(-5V)I1

I3,

Blue

Red

Green1

I(-5)

Green2

C1

C2

I(0)

Curr

ent (

A)

Time (ms)

-4 -3 -2 -1 0 1 2 3 4-6

-5

-4

-3

-2

-1

0

1

2

3

4

V(Q1)

V(Q2)

I3,I4

I2

I1

B

C

D

E

F

G

H

I

J

K

L

M

V (

Q1;Q

2)

V

Time (ms)

B

C

D

E

1221 )()( CtiCti CC -

dt

dvCtiC

2,1

2,12,1 )(

Current&Voltage (SPICE simulation)

Blue the emiter-base of Q1 becomes optically forward biased and C2 is rapidly charged in inverse polarity of C1

Red changes, in the opposite way.

Green the current is the balance between the blue- and the red-like contributions

I4

Q2

I1 1

I2

Q1

C2 R2 R1 (V)

C1 I3

I(C1)

I(C2)

V(Q1)

V(Q2)

I4

Q2

I1 1

I2

Q1

C2 R2 R1 (V)

C1 I3

NUMERICAL SIMULATION

ac equivalent

electrical circuit

MATLAB as a programming environment and the four order Runge-Kutta method to solve the state equations

)(1

1

)(111

11

2,1

2

12,1

222121

11112,1ti

c

ctv

crcrcr

crcr

dt

dv

--

-

tvr

ti 2,1

2

10

0.0 1.0 2.0 3.0 4.0 5.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5 i(R

1=10MW,R

2=5kW)

i(R1=1kW,R

2=5kW)

I1=0.32

I2=1.1

I3=1.1

I4=0.82

C1/C

2=2.5

V=+1V

V=-8V

C

I -8V

IR

IGR

IGB

IB

I(+1=

Ph

oto

cu

rre

nt

(A

)

Time (ms)

0.000 0.001 0.002 0.003 0.004 0.005

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

B

C

0.0 1.0 2.0 3.0 4.0 5.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5 i(OFF)

R1=10MW

R2=5kW

i(ON)

I1=0.32

I2=1.21

I3=0.54

I4=0.82

C1/C

2=2.5

=0

=73mWcm-2

=554 nm

C

I -8V

IR

IGR

IGB

IB

Ion

dif

Ph

oto

cu

rre

nt (

A)

Time (ms)

0.000 0.001 0.002 0.003 0.004 0.005

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

iOFF

-iON

B

C

D

I2

15u

I

I II

C2

1000p

I

0

Q1 V

Q2

I

I1

15u

C1

2500p

I3

10u

I4

8u

I

I2

15u

I

I II

C2

1000p

I

0

Q1 V

Q2

I

I1

15u

C1

2500p

I3

10u

I4

8u

I

THEORETICAL MODEL

1221 )()( CtiCti CC -

Negatively biased

Positively biased

M A Vieira, M. Vieira, M. Fernandes, A. Fantoni, P. Louro, M. Barata, Amorphous and Polycrystalline Thin-Film Silicon Science and Technology — 2009, MRS Proceedings Volume 1153, A08-03

400 450 500 550 600 650 700 750 8000.00

0.05

0.10

0.15

0.20

#1

#1b

#1a

L =0

#1

L =2mWcm

-2

#1a#1b

Sen

siti

vit

y (

A/W

)

Wavelength (nm)

CONCLUSIONS Single and stack a-SiC:H pin devices were compared under different

optical and electrical bias conditions and readout techniques.

400 500 600 700 8000.0

0.1

0.2

0.3

0.4 pi(a-SiC:H)n/pi(a-Si:H)n

-10 V

+3 V

Ph

oto

cu

rre

nt (

a)

Wavelength (nm)

B

B

B

B

B

B

B

B

B

B

B

B

B

B

GlassITO

P

i-Si:H (1000 nm)

nITO

GlassITO

P

i-Si:H (1000 nm)

nITO

GlassITO

P

i’-SiC:H (200 nm)

#2a

nP

i-Si:H (1000 nm)

nITO

ITO

Gla

ss p

i’(a-S

iC:H

)

i (a

-Si:H

)

n p nIT

O

ITO

Gla

ss p

i’(a-S

iC:H

)

i (a

-Si:H

)

n p nIT

O

ITO

Gla

ss p

i’(a-S

iC:H

)

i (a

-Si:H

)

n p nIT

O

ITO

Gla

ss p

i’(a-S

iC:H

)

i (a

-Si:H

)

n p nIT

O

LSP

WDM

Readout techniques

0.0 1.0 2.0 3.0 4.0 5.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

R+G+B

B[10101010]

G[10011001]

R[01111000]

V=+1V

V=-8V R&G&B

G

BR

B (-8V)

R(-8V)

G(-8)

B(+1)

R(+1)

G(+1)

Led R

Led G

Led B

soma

+1V

-8V

Ph

oto

cu

rre

nt

(A

)

Time (ms)

CONCLUSIONS If a light scan with a fixed wavelength is

used to readout the generated carriers it can recognize a color pattern projected on it, acting as a color and image sensor.

-6 -5 -4 -3 -2 -1 0 1 2

-8x10-8

-6x10-8

-4x10-8

-2x10-8

0

b)

a)

S=650 nm

(pin/pin)

whithout

optical bias

L=550 nm

L=650 nm

L=450 nm

Photo

curr

ent (A

)

Voltage (V)

If the photocurrent generated by different monochromatic pulsed channels or their combination is readout directly, the information is multiplexed or demultiplexed.

When triggered by light with appropriated wavelengths, it can amplify or suppress the generated photocurrent working as an optical amplifier.

0.0 0.3 0.5 0.8 1.0 1.30.0

0.5

1.0

1.5

2.0

Dark

V=+1V V=-8V

L=0

RL

=626nm

GL

=524nm

BL

=470nm

S=626 nm

Photo

curr

ent (

)A

Time (ms)

B

D

E

F

C

G

H

I

Three integrated transducers in one single photodetector

TEAM Manuela Vieira Alessandro Fantoni Paula Louro Miguel Fernandes Yuri Vygranenko João Costa Manuel Barata Manuel A. Vieira António Maçarico João Martins Vitor Fialho Donatello Brida Victor Silva Reinhard Schwarz Manfred Niehus

A group of experienced and young researchers covering the areas of materials and devices processing; materials and devices characterization and optimization, well supported by the physics modelling of the devices and the corresponding software for information extraction

Thanks for your attention