Methods and Materials for Remote Sensing: Infrared Photo-Detectors, Radiometers and Arrays

163 Pages·2004·10.73 MB·English

by  Yuri Abrahamian

METHODS AND MATERIALS FOR
REMOTE SENSING
Infrared Photo-Detectors, Radiometers
andArrays
METHODS AND MATERIALS FOR
REMOTE SENSING
lnfrared Photo-Detectors, Radiometers
andArrays
Yuri Abrahamian
Armenian National Academy of Sciences
Ashtarack, Armenia
Radik Martirossyan
Ferdinand Gasparyan
Yerevan State University
Yerevan, Armenia
Technical Editor:
Karen Kocharyan
Tufis University
Medford, MA, U.S.A.
SPRINGER. SCIENCE+BUSINESS MEDIA, LLC
Library of Congress Cataloging-in-Publication Data
Methods and Materials for Remote Sensing
Infrared Photo-Detectors, Radiometers and Arrays
Yuri Abrahamian. Radik Martirossyan. Ferdinand Gasparyan. Karen Kocharyan
ISBN 978-1-4613-4762-0 ISBN 978-1-4419-9025-9 (eBook)
DOI 10.1007/978-1-4419-9025-9
Translated by Moses Fayngold
Copyright © 2004 by Springer Science+Business Media New York
Originally published by Kluwer Academic Publishers in 2004
Softcover reprint of the hardcover 1s t edition 2004
AH rights reserved. No part of this work may be reproduced. stored in a retrieval
system, or transmitted in any form or by any means, electronic, mechanical,
photocopying, microfilming, recording, or otherwise, without prior written
permission from the Publisher, with the exception of any material supplied
specifically for the purpose of being entered and executed On a computer system,
for exclusive use by the purchaser of the work.
Printed on acid1ree paper.
Contents
Preface Vll
1. PHOTOELECTRIC AND NOISE CHARACTERISTICS
OF PHOTODETECTORS
1.1 Introduction 1
1.2 GenerationofFreeCarriersinSemiconductors 6
1.3 Photoelectric CharacteristicsofResistivePhotodetectors 13
1.4 Photodetectors withP-NJunction 17
1.5 Elements oftheTheory ofRandomProcesses 22
1.6 Internal NoiseinPhotodetectors 31
1.7 Concepts ofNoiseCoefficientandNoiseTemperature 41
1.8 Thermal andQuantumNoises.ElementsofMicrowave
Radiometry 45
2. PHYSICAL PRINCIPLES OF INFRARED
RADIOMETRIC SYSTEMS
2.1 BasicCharacteristicsofIR-Detectors 51
2.2 Threshold CharacteristicsofPhotodetectors 53
2.3 ThresholdCharacteristicsofIRDetectorsand
IR-RadiometerDesignPrinciples 63
2.4 IR-RadiometerwithExternalModulation 72
2.5 IR-RadiometerswithInternalModulation 79
2.6 Methods ofCalibrationofIR-RadiometericSystems 86
3. GROWING TECHNOLOGY AND ELECTRO
PHYSICAL CHARACTERISTICS OF SOLID
SOLUTIONS PbSnTe, PbSnSe and CdHdTe
3.1 Introduction 93
3.2 Physico-ChemicalPropertiesofSolidSolutions
Pbj_xSnxTe,Pbj_xSnxSe,and CdxHgj_xTe 94
3.2.1 PbTe- SnTe (PbxSnxTe) 94
VI METHODS AND MATERIALS FORREMOTE SENSING
3.2.2 PbSe-SnSe (Pbj.ySnySe) 99
3.2.3 CdTe-HgTe (CdxHgj.xTe) 101
3.3 Technology for Growing the Single Crystals,
Epitaxial Films, andPhoto-DiodeStructures 104
3.4 GrowingSingle Crystals of Pbj.xSnxTe,
[(Pbj.xSnx)j.y!ny]Te and [(Pbj.xSnx)j_yCdy]Te 110
3.4.1 PolycrystallineMaterial 110
3.4.2 Growingthe Single Crystals of Pbj.xSnxTe
and Pbj.xSnxTe<ln,Cd> 115
3.4.3 Electrical andStructural Characteristics
ofSingle Crystals 118
3.4.4 Technology for Growingthe Epitaxial Films of
Pbj.xSnxTe,andPbj.xSnxTe<ln> 120
3.5 Multi-ElementPhotodetectors
3.5.1 LinearArrays of Pbi..Sn.TePhoto-Diodes 125
3.5.2 Photo-Conductivity of Pbj_xSnxTe<ln>
=
at Microwaves (:A, 4-5 mm) 129
3.5.3 Lineararrays ofphotosensitive field-effect
transistors witheasily reproducible technology 132
References 143
Index 157
Preface
Currently underway is an active search and development ofmethods
and advanced techniques for the measurement ofweak:signals using
photosensitive media, such as complex semiconducting compounds,
super-lattices, avalanche photo-diodes, and coupled charge devices.
Thisbookpresentsthebasicprinciplesandtheguidelinesforthedesignof
IR and microwave radiometers intended for the detection of weak
electromagneticsignalsinanoisybackground.
Significant attentionis paidin this book to the discussionof the origin of
the noisesandconsiderationofthephysicalfactorslimitingthe sensitivity
of photo sensors.Brieflyare discussedthe physico-chemicalpropertiesof
narrow-band semiconductors Pbj_xSnxTe, Pb..Sn.Se and CdxHgj.xTe,
which are the basic photosensitive materials for the microwave and IR
radiometry.Alsodescribedarethemethodsforgrowingthesinglecrystals,
epitaxialfilmsand arraysfromsolidsolutionsofthese compoundsfor the
applicationinphotosensitivedetectors.
The main goal ofthis book is to present the entire material from the
unifying physical viewpoint, which will be helpful for the designers
ofphoto-detecting devices, and professionals contributing in various
areas of remote sensing. The book is also useful for the specialists
working on the development ofIR systems. In the authors' opinion,
the subjects discussed in this book complete a gap existing in the
technical literaturebetween the microwave and IR radiometry.
Chapter 1
PHOTOELECTRIC AND NOISE
CHARACTERISTICS OFPHOTODETECTORS
1.1 Introduction
The recent achievements in remote sensing of the Earth's surface and
atmosphere, as well as of the planets, became possible due to
implementation of radars and radiometric systems, which are capable of
distinguishing a weak electromagnetic radiation ina noisy background and
because ofsuccessful development ofsensitive microwave, millimeterand
submillimeter wave detectors [1-22]. The detection ofthe remote objects,
the measurement of their coordinates, the determination of their shapes
and forms is usually realized with the methods ofoptical location. There
are known two types of electromagnetic location - active and passive
location.
Theactive location is based on the detection ofsignal reflected back from
an irradiated object. Such systems, particularly operating at microwave
frequencies, usually are too large and consume too much power.
Thepassive location (or, otherwise, the radiometry) relies on the accurate
measurementofthe thermal radiation power emanated byan object.
Currently, the systems of passive location can be attributed either to the
radiothermal location systems, which operate in atmospheric windows
(wavelengths from millimeters to tens of meters [5-7]), or ,to IR
radiometers, which are using the infrared radiation in the range of
wavelengths from 0.7 to 15micrometers [1-4]. Essential peculiarity ofthe
passive location systems operating inthe microwave range isthe similarity
between the spectrum ofsignal and the noise spectrum ofthe measuring
receiver. Therefore, the problem ofthe microwave radiometry eventually
comes to distinguishinga small extrasignal on the background ofthe noise
signal permanently presenting inthe receiver input.
In IR radiometry there is no such similarity. Therefore, it is required to
apply individual approach in designing the circuitry for the detection of
weak IR signals by taking into account the differences in spectra ofthe
Y. Abrahamian et al., Methods and Materials for Remote Sensing
© Kluwer Academic Publishers 2004
2 METHODS AND MATERIALS FOR REMOTE SENSING
received signal and the noise, the peculiarities ofthe noise characteristics
and other parameters of the specific photodetectors, including response
time, bandwidth, photosensitivity and etc. [8-11]. In IR-radiometry,
including the active location, it is possible to decrease the contribution
from the background noise by decreasing the angular resolution from its
maximum value determined by the aperture-to-wavelength ratio. In
general, by using the methods ofIR radiometry, including photo-electronic
devices, it is possible to increase the resolution, to reduce the sizes and
weight to the limits that are out ofthe reach by any other remote sensing
systems.
Figure 1.1shows the part ofelectromagnetic wave spectrum used inphoto
electronic remote sensing systems [13]. The wavelength range 'A = 0.38
3.0Jlcorresponds to the reflection spectrum. The energy received in this
wavelength range isbasicallythe solar radiation and the radiation reflected
Opticalwavelengthsscale
Thermalor
emitting
.p..:.:. I
I
Visible :~z II MIiRddle II FarIR
I
11 tI
0.300.38 0.72 1.3 3.0 7.0 15.0
Wavelength(urn)
Figure1.1. Spectrumofelectromagneticradiation [13].
back from the terrestrial objects. The IR spectrum extends from the visible
spectrum (A. = O.72Jl) and up to the microwaves (A. ~ 1000Jl). This
spectrum conventionally may be split into four sub-bands: near IR, with 'A
=0.72 -1.3u; middle IR, with 'A = 1.3 - 3u;far IR, with A.=3 - 15Jland
extreme IR with A.> 15Jl.The first three sub-bands are used predominantly
for atmospheric observations. The areas of atmospheric windows and
opacities inthis frequency range are shown inFigure 1.2.Because ofvery
strong absorption in the atmosphere, the electromagnetic waves of the
extreme IR range are used exclusively in the short-distance laboratory
CHAPTER 1 3
measurements. The sensittvtty spectra, D'A: for some common
photodetectors intherange ofatmospheric windows areshown inFigures
l.3a and l.3b.
NearIR MiddleIR FarIR
100
*'
80
I=l
..0...
60
..V..J.
VeJ
40
VJ
~
~ 20
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Wavelength(urn)
Figure!. 2.Thespectralcharacteristicsofatmosphere[12].
'10"
~
~
E
(.;)
.'"
o
10'"
:3 4 5 6 7 8 910 11 12
Wavelength (urn)
Figure!. 3a.Thedetectivityspectraforvarious IR-detectorswith intrinsicconductivity.
4 METHODS AND MATERIALS FOR REMOTE SENSING
The problem of developingthe highly sensitive IR radiometric systems
depends not only on the designof circuitry intended for measurement of
weaksignals,butalsoontheadvancement indevelopment of IRreceivers
with high detective power at the frequencies corresponding to the
atmospheric windows(A=0.95-1.05,u; 1.2-1.3,u; 1.5-1.58,u; 2.1-2.4,u; 3.3
4.2,u; 4.5-5.1,uand 8-13,u[14D. Hereitisappropriate mentioning, thatthe
radiation in the range A=7-15,u is emanated by the background objects
havingthetemperature closetothetemperature atthesurfaceoftheEarth
(T= 300K).
10"
IT=300'K! 10"
I
Tcl95"KI
~10" ~ 10" 2
ill
E
E
u~
Q10" .q, 10"
0
InSb
A
10'
0 2 4 6 8 10 x.um
10'
0 2 4 6 8 10 A,}lm
10"
~
10"
~
e: 10"
g~
E s:±! 2
.u'" E
0 .o"
10" o 10"
20 4 6 8 10
Figure 1.3b.Thespectra ofdetectivityofthedetectors atvarious temperatures
.Progress in application of IR radiometric systems started in 70-s when
highly sensitive photodetectors, based, particularly, on ternary