Workshop PHOTOTRANSISTORS Septembre 9, 2003, Budapest / Hungary C. Gonzalez 1 Workshop «...

Workshop PHOTOTRANSISTORS Septembre 9, 2003, Budapest / Hungary C. Gonzalez 1

Workshop « Phototransistors »September 9, 2003 Budapest Hungary

InP-based Phototransistors and comparison of performances to those of

PIN and UTC photodiodes

Carmen Gonzalez

Alcatel R&I - Laboratoire OPTO+Carmen. [email protected]


Outline

InP/InGaAs-based bipolar phototransistor

Photo-HBT performances as a direct photodetector

Optoelectronic integrated circuits OEIC:- O/E narrow band amplifier- O/E upconverting mixers

Performances of:- Top illuminated PIN photodiode- Back illuminated UTC photodiode

Summary


Choice of material to maximize carrier velocities

Material System : InP (despite of cost) vs GaAs

InP, InGaAs : Higher electron velocities and lower surface recombination velocities than GaAs

InGaAs : Narrow band gap Eg = 0.75 eV, compatible with the detection of 1.30 and 1.55 µm wavelength light

Photo-HBT developed at OPTO+


Photo-HBT developed at OPTO+

Layer Growth : Chemical Beam Epitaxy

Base Layer : Carbon doped Low diffusion coefficient

Compositionally graded-base InxGa1-XAs

Vertical structure Key technology : epitaxy

• no antireflection layer


Emitter area : 9 µm2

Base area : 44 µm2

Optical window area : 16 µm2

-20

-15

-10

-5

0

5

10

15

20

25

1,00E+08 1,00E+09 1,00E+10 1,00E+11 1,00E+12

Frequency (Hz)

Ph

oto

resp

on

se (

dB

)

20 dB/decade

FC = 110 GHz

FCPD-mode

Tr-mode

Gopt = 32 dB

Photo-HBT as a direct photodetector

1A/W

R(A/W)20.LogR(dB)

RDC = 0.2 A/W


Saturation characteristics

Photo-HBT saturation at 19 GHz

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15 -10 -5 0 5

Pavg (dBm)

RF

ou

tpu

t p

ow

er

(dB

m)

-1 dBTr-mode

@ -1dB: -21 dBm


photo-HBT CHAIN

Spectrum

Analyser

32C

E

B1

<Iin

>

Ib_ tot

Ib_ tot =I b_ elec + Iph

LNAb-tee

G = 50 dB

NF < 5 dB Psys_noise

(dBm/Hz)

RBW = 2 MHz

Analog noise characteristics

Input noise current spectral density <Iin> (pA/Hz^0.5)


Analog noise characteristics

Input noise current spectral density

@ 40 GHz: Ic <Iin> (mA) (pA/Hz^0.5)

2 50 10 66

0

10

20

30

40

50

60

70

80

1,00E+09 1,00E+10 1,00E+11

Frequency (Hz)

<Ii

n>

(p

A/H

z^0.

5)

36 pA/Hz 0̂.5@28 GHz

51 pA/Hz 0̂.5@28 GHz

28 GHz

Ic = 10 mA

Ic = 2 mA


Data signal : 25 Mb/s, 16 QAM

1,E-11

1,E-10

1,E-09

1,E-08

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

1,E-02

10 15 20 25 30C/N (dB)

BE

R

@ 27.875 GHz

@ 800 MHz

photo-HBT at 27.875 GHz

Pavg = -5,5 dBm

R = 0.35 A/WIc = 10.3 mA

Digital noise characteristics

BER at 10-9: C/N = 24.3 dB

Laser 1.55 m

Photo-HBT

Opticalattenuator

EOM 5 dBm

LNA

MPG2 Generator

16 QAMmapping

I Qmodulator1.6 GHz

OL29.475 GHz

Filtre27.875 GHz

BERmeasurements

OL2.4 GHz

OL29.475 GHz

27.875

GHz

1.6 GHz800 MHz30 dB


OEIC using photo-HBTs

-25

-15

-5

5

15

25

35

45

55

10 15 20 25 30 35 40

Frequency (GHz)

TZ

Gai

n (

dB

Oh

m)

GTZ @ 28 GHz = 50 dBOhm

4 GHz

Photodetection at 27.875 GHz

1,E-12

1,E-11

1,E-10

1,E-09

1,E-08

1,E-07

1,E-06

1,E-05

1,E-04

1,E-03

14 16 18 20 22 24 26 28C/N (dB)

BE

R PINPavg = 1 dBm

photo-HBT circuitPavg = -5 dBm

Data signal : 25 Mbit/s 16 QAM

PhotoHBT

/4 line

CB VC

E

OutIn

IB

h

RBp

ol

An O/E narrow-band amplifier at 28 GHz: 2 cascode cells with 1 photo-HBT+3HBTs

Transimpedance Gain = 50 dB @ 28 GHz

BER at 10-9: 24.3 dB


B B B B

PLOPRF

Cascode cells28 GHz

Photo-HBT

B B

PLO PRF

Chip size : 1634 x 1300 µm2

42 GHz

Chip size : 2850 x 1600 µm2

Optoelectronic mixers using photo-HBTs

Upconversion mixer from 2 GHz to 28 GHz and to 42 GHz

HBTphotoPDmodeout

circuitoutconv

)(IFPIF)(LOP

G

Gconv

28 GHz 17.8 dB

42 GHz 9.2 dB

Mixer


Top illuminated PIN photodiode

P

I

N

Trade-off between efficiencyand speed (bandwidth)The better performances with aPhotoabsorption layer of 400nm: Bandwidth = 30 GHz R = 0.30 A/W

Photoabsorption layer

The main attraction of this device is itscompatibility for integration with SHBTs.For example, this photoreceiver realized byD. Huber et al., IEEE JLT 2000

P+:InGaAs

InGaAs

N+:InGaAs

SHBT Base-collector homojunction = PIN homojunction Bandwidth = 53 GHz Transimpedance gain = 44.3 dB

PINphotodiode

SHBT-based preamplifier


PIN photodiode

For higher-speed operations, waveguide or travelling-wave photodiodes

are proposed. TW-PD with bandwidth of 100 GHz has been reported.

However, photoreceivers based on edge-coupled PIN PDs exhibit similar

characteristics to those obtained with top-illuminated PIN-PD

Top-illuminated phototransistors, which offer internal gain, could greatly

reduce the need for preamplification, with circuits less complicated than

those associated to PIN PD, in particular at millimeter wave frequencies.


In high-speed optical systems optical pre-amplifier can be installed directly in front of the photoreceiverNeed of photodiodes with broad bandwidth, high responsivity and high output power

Back illuminated UTC photodiode

p-Contact Subcollector

Barrier

Basep+p+

p+

Collectorn

n+

Opticalabsorption region

Space-chargeregion

CB

VB

+

-Uni-traveling-carrier photodiode principle

Separate absorption and space-charge region:

high carrier density

Electrons only contribute to drift current:

transit time improved

Proposed by T. Ishibashi et al., NTT, 1997


Back illuminated UTC photodiode

p+ : Base contact

p+ : Barrierp+ : Base

absorption layer

Composite collector

Sub-collector

InP-Substrate

Thickness (nm)

Responsivity (A/W)

Bandwidth (GHz)

Vpp (V)

Collector Base 208 140 140

0.16 A/W

0.16 A/W

152 GHz 114 GHz 125 GHz

0.65 V 1.9 V 0.6 V

Since UTCs require a thin absorption layer:

Responsivity is relatively low* < 0.2 A/W

Need of edge-illumination for improving R

*The responsivity is generally the same as that of a PIN-PD for the same absorption layer thickness

Shimizu et al. IEEE PTL, vol 10, pp. 412, 1998


Light

Thickness (nm)

Responsivity (A/W)

Bandwidth (GHz)

Collector Base 200 280

0.43 A/W

54 GHz

Output power dependance on input light

UTC photo-HBT 20 GHz 19 GHzPopt 2.5 dBm 2.5 dBmPRF -30 dBm -21 dBm

UTC refracting-faced photodiode

To achieve higher responsivity in edge illuminated configuration

Fukushima et al. EL, vol 37, pp 780-781, 2001


Summary - Future prospect

High speed photo-SHBT based on InP technology

Frequency performances up to the mm-wave band

Compatible with SHBT technology for monolithically

integrated photoreceivers (amplifiers, mixers, oscillators)

It is well suited for performing more complex O/E functions, as mixing

or selft-oscillation, at high frequency and high bit rates

Workshop PHOTOTRANSISTORS Septembre 9, 2003, Budapest / Hungary C. Gonzalez 1 Workshop «...

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