A Bias-Dependent Equivalent-Circuit Model of Evanescently Coupled Photodiode (ECPD) Advisers : J.- W. Shi, Y.- J. Chan Student : Y.- S. Wu

A Bias-Dependent Equivalent-Circuit Model of Evanescently Coupled Photodiode (ECPD)

Advisers : J.- W. Shi, Y.- J. Chan

Student : Y.- S. Wu

National Central UniversityNational Central University

Micro-Optoelectronic LabsMicro-Optoelectronic Labs

TaiwanTaiwan

IV. Model Extraction

I. Motivation

III. Measurement System

II. The Structure of ECPD

V. The Fitting Results

VI. Conclusions

Outline


I. Motivation




VI. Conclusions

+

Transmitter for Fiber-Radio Communication System

+ mm-Wave Detector

Photodiode Matching Circuit Antenna

Transmitter Module

The loss of electrical signal can be reduced through wireless

communication system.

To simplify the base station by eliminating the costly post amplifiers

and cables.

+

Transmitter for Fiber-Radio Communication System

+ Mm-Wave Detector

Photodiode Matching Circuit Antenna

Transmitter Module

The loss of electrical signal can be reduced through wireless

communication system.

To simplify the base station by eliminating the costly post amplifiers

and cables.The model extraction of PD serves as a key approach to design the transmitter module


I. Motivation




VI. Conclusions

Epi-Layer structure

ECPD

Geometric structure

ECPD: Three major target can be achieved simultaneously

Epi-layer structure: Partially p-doped photo-absorption layerGeometric structure: Evanescently coupled waveguide

The ECPD We Used in Our Model Extraction!!

0 10 20 30 40 50-20

-15

-10

-5

0

5

10

-1V -3V -5V

Frequency (GHz)

Rel

ativ

e R

espo

nse

(dB

) Photocurrent: 2mA

Active area: 200m2

Electrical Bandwidth (with Different Reverse Bias )

The measured frequency responses of device A under three different dc bias voltages.

1 10-25

-20

-15

-10

-5

0

5

10

100m2

150m

200m2

DC photocurrent (mA)

40 G

Hz

Outp

ut R

F P

ow

er

(dB

m)

f= 40GHzBias voltage: -5V

(23mA, 6.5dBm)

RF power versus dc photocurrent of ECPD for different reverse at 40GHz.

High Power Performance


I. Motivation




VI. Conclusions

Heterodyne-Beating Measurement Setup (Large Signal Measurement)

Bias Tee

Mechanical Pump

(fasten the sample)

Power supply & current meter

Polarization controller

EDFA (for high power generation )

Coupler

Polarization controller

Tunable laser

Tunable laser

OM

Power meter

Spectrum (for high frequency 40GHz)

Holder

Piezoelectrical stage

sample

Fiber

electric cord (DC)

electric cord (AC)-

By increasing the wavelength difference, the bandwidth response is available through recording the amplitude of RF tone signal.

Can measure the BW response and power generation

LNA Measurement Setup (Small Signal Measurement)

Port 1

Port 2

EDFA

Power supply

Tunable Laser

Polarization Controller

Polarization Controller

1. Calibrate the packaged Modulator and save as s2p file

2. Don’t change the bias voltage & polarization of the Modulator

3. De-embedded the Modulator

Lightning Network Analyzers

Step 1

Step 2

Modulator

Not only measure amplitude response but also phase response

Anritsu 37300C VNA + MN4765A (commercial PD)


I. Motivation




VI. Conclusions

Rs

Z=50 ΩCpCsc

Rt

CtCdxCj

L

RC delay time region (fRC)

Space charge screen effect reg

ion (fsc)

The Equivalent Circuit Model

Transit time region (ft)

G=0.013 S

Z=50 Ω

The frequency response can be determined by three major factors

Gang Wang, and Tsuneo Tokumitsu, IEEE Trans. Microwave Theory Tech., 15 (2003) 1227.

Rs

Z=50 ΩCpCsc

Rt

CtCdxCj

L


G=0.013 S

Z=50 Ω

S22

The components in right hand of the equivalent circuit can be verified by fitting the S22 parameter.

Electrical signal

Electrical signal

Rs

Z=50 ΩCpCsc

Rt

CtCdxCj

L


G=0.013 S

Z=50 Ω

S22

S21

All the components in the equivalent circuit can be verified by fitting the S21 parameter.

Space charge screen effect region (fsc)

Transit time region (ft)

Optical signal Electrical signal

Rc Contact Resistance

Rj Junction Resistance

Cj Junction Capacitance

Cdx BCB Capacitance

Cp Pad Capacitance

Lg Inductance of Contact Metal

Ls Inductance of Pad

The Definition of Parameters in This Equivalent Circuit

The Step of Model Extraction!!

Part 1 : Determine right hand of equivalent circuit

Measure the S22 parameters of ECPD

Frequency (50MHz to 40GHz)M

easu

red

S22




Measure the S22 parameters of

coplanar electrical pad

Frequency (50MHz to 40GHz)

PA

D M

easu

red

S22




Measure the S22 parameters of copl

anar electrical pad (L, Cdx, Cp)

Cdx Cp

L




Measure the S22 parameters of cop

lanar electrical pad (L, Cdx, Cp)

Perform the I-V measurement

-3 -2 -1 0 1 2

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Cu

rren

t (m

A)

Bias Voltage (V)

I-V Curve

Differential Resistance : 150ohm






Perform the I-V measurement (Rs)

Rs







Perform the C-V measurement (total capacitance)

-3 -2 -1 0-100

-50

0

50

100

150

200

250

Cap

acit

ance

(fF

)Bias Vlotage (V)

C-V Curve

Average Capacitance : 79 fF







Perform the C-V measurement (total capacitance)

Cj


Part 2 : Determine left hand of equivalent circuit

Measure the S21 parameters of ECPD under different

photocurrent and bias voltage 0 10 20 30 40 50

-20

-15

-10

-5

0

5F

req

uen

cy R

esp

on

se (

dB

)

Frequency (GHz)

-1V -3V -5V

Active Area : 150 m2

Photocurrent : 4 mA

0 10 20 30 40 50-20

-15

-10

-5

0

5

F

req

uen

cy R

esp

on

se (

dB

)

Frequency (GHz)

0.2mA 2mA 4mA


Bias Voltage : -1 V




photocurrent and bias voltage

Fit the S21 parameters under high bias voltage and low photocur

rent (Rt, Ct)

Rt

Ct




photocurrent and bias voltage

Fit the S21 parameters under high bias voltage and low photocur

rent (Rt, Ct)

Fit the S21 parameters under low bias voltage and high photocurrent (Csc)

Csc


I. Motivation




VI. Conclusions

The Fitting Result of S22 Parameter

The demonstrated model can fit well with the measurement result that obtained under -3V bias voltage with 150 μm2 active area.

0 10 20 30 40 50 60 70-20

-15

-10

-5

0

5

S (-1V) S (-3V) S (-5V)

Fre

qu

ency

Res

po

nse

(d

B)

Frequency (GHz)

M (-1V) M (-3V) M (-5V)


Photocurrent : 4 mA


The space charge screen effect will reduce as the bias voltage increases !!

0 10 20 30 40 50 60 70-20

-15

-10

-5

0

5

S (0.2mA) S ( 2mA) S ( 4mA)

Fre

qu

ency

Res

po

nse

(d

B)

Frequency (GHz)

M (0.2mA) M ( 2mA) M ( 4mA)


Bias Voltage : -1 V


The space charge screen effect is very obvious under low bias voltage and high current generation.

-5 -4 -3 -2 -1-50

0

50

100

150

200

250

Csc (4mA) Csc (2mA) Csc (0.2mA)


CS

C (

fF)

Bais Voltage (V)

The Bias & Photocurrent-Dependent Csc Parameter

The device speed performance won’t degrade under high bias voltage as the photocurrent increases due to the elimination of space-charge capacitance.


I. Motivation




VI. Conclusions

Conclusions

By concerning the relationship between

the influence of bias voltage and

photocurrent in the equivalent circuit-model

of high power PD, such model is more

convenient for systems and circuits

integration especially under high RF power

applications.

0 10 20 30 40 50-20

-15

-10

-5

0

5

Fre

qu

ency

res

po

nse

(d

B)

Frequency (GHz)

Simulated 01mA Simulated 20mA Measured 01mA Simulated 20mA


Bias Voltage : -5 V

About 35GHz

freq (40.00MHz to 50.00GHz)

Sim

ula

ted

20

mA

S

(2,2

)S

imu

late

d 1

mA

S

(2,2

)

Frequency (0.0000 Hz to 50.00GHz)

Measu

red

1m

A S

(2,2

)M

easu

red

20

mA

S

(2,2

)

Bias Voltage -5V

J. W. Shi and Y. S. Wu, IEEE Photon. Technol. Lett., 17 (2005) 1929.High-Speed, High-Responsivity, and High-Power Performance of Near-Ballistic

Uni-Traveling-Carrier Photodiode at 1.55m Wavelength

The Model Extraction of BUTC Under High Photocurrent

Documents

A Bias-Dependent Equivalent-Circuit Model of Evanescently Coupled Photodiode (ECPD) Advisers : J.- W. Shi, Y.- J. Chan Student : Y.- S. Wu