Infrared detectors: status and trends

doi:10.1016/S0079-6727(02)00024-1

Progress in Quantum Electronics

Volume 27, Issues 2–3, 2003, Pages 59-210

https://doi.org/10.1016/S0079-6727(02)00024-1 Get rights and content

Abstract

At present efforts in infrared detector research are directed towards improving the performance of single element devices, large electronically scanned arrays and higher operating temperature. Another important aim is to make IR detectors cheaper and more convenient to use. All these aspects are discussed in this paper.

Investigations of the performance of infrared thermal detectors as compared to photon detectors are presented. Due to fundamental different types of noise, these two classes of detectors have different dependencies of detectivities on wavelength and temperature. Next, an overview of focal plane array architecture is given with emphasise on monolithic and hybrid structures. The objective of the next sections is to present the status of different types of detectors: HgCdTe photodiodes, Schottky-barrier photoemissive devices, silicon and germanium detectors, InSb photodiodes, alternative to HgCdTe III–V and II–VI ternary alloy detectors, monolithic lead chalcogenide photodiodes, quantum well and quantum dot infrared photodetectors.

Final part of the paper is devoted to uncooled two-dimensional arrays of thermal detectors. Three most important detection mechanisms, namely, resistive bolometer, pyroelectric detectors and termopile are considered. The development of outstanding technical achievements in uncooled thermal imaging is also presented.

Introduction

Looking back over the past 1000 years we notice that infrared (IR) radiation itself was unknown until 202 years ago when Herschel's experiment with thermometer was first reported. He built a crude monochromator that used a thermometer as a detector so that he could measure the distribution of energy in sunlight. In April 1800 he wrote: [1]

“Thermometer No. 1 rose 7 degrees in 10 minutes by an exposure to the full red coloured rays. I drew back the stand....... thermometer No. 1 rose, in 16 minutes, 8 3/8 degrees when its centre was 1/2 inch out of the visible rays.”

The early history of IR was reviewed about 40 years ago in two well-known monographs [2], [3]. The most important steps in development of IR detectors are the following:

•
in 1921 Seebeck discovered the thermoelectric effect and soon thereafter demonstrated the first thermocouple,
•
in 1829 Nobili constructed the first thermopile by connecting a number of thermocouples in series [4].
•
in 1833 Melloni modified design of thermocouple and used bismuth and antimony for it design [5].

Langley's bolometer appeared in 1880 [6]. Langley used two thin ribbons of platinum foil, connected so as to form two arms of a Wheatstone bridge. Langley continued to develop his bolometer for the next 20 years (400 times more sensitive than his first efforts). His latest bolometer could detect the heat from a cow at a distance of quarter of mile. Thus, at the beginning the development of IR detectors was connected with thermal detectors.

The photon detectors were developed in XX century. The first IR photoconductor was developed by Case in 1917 [7]. In 1933, Kutzscher at the University of Berlin, discovered that lead sulphide (from natural galena found in Sardinia) was photoconductive and had response to about 3 μm [8].

Many materials have been investigated in the IR field. Observing a history of the development of the IR detector technology, a simple theorem, after Norton [9], can be stated: All physical phenomena in the range of about 0.1–1 eV can be proposed for IR detectors. Among these effects are: thermoelectric power (thermocouples), change in electrical conductivity (bolometers), gas expansion (Golay cell), pyroelectricity (pyroelectric detectors), photon drag, Josephson effect (Josephson junctions, SQUIDs), internal emission (PtSi Schottky barriers), fundamental absorption (intrinsic photodetectors), impurity absorption (extrinsic photodetectors), low dimensional solids [superlattice (SL) and quantum well (QW) detectors], different type of phase transitions, etc.

Fig. 1 gives approximate dates of significant development efforts for the materials mentioned. The years during World War II saw the origins of modern IR detector technology. Photon IR technology combined with semiconductor material science, photolithography technology developed for integrated circuits, and the impetus of Cold War military preparedness have propelled extraordinary advances in IR capabilities in just a fraction of the last century [10].

Section snippets

Historical aspects of modern infrared technology

During the 1950s IR detectors were built using single-element-cooled lead salt detectors, primarily for anti-air-missile seekers. Usually lead salt detectors were polycrystalline and were produced by vacuum evaporation and chemical deposition from a solution, followed by a post-growth sensitisation process [8]. The first extrinsic photoconductive detectors were reported in the early 1950s. Since the techniques for controlled impurity introduction became available for germanium at an earlier

Classification of infrared detectors

Spectral detectivity curves for a number of commercially available IR detectors are shown in Fig. 2. Interest has centred mainly on the wavelengths of the two atmospheric windows 3–5 μm [middle wavelength IR (MWIR)] and 8–14 μm (LWIR region) (atmospheric transmission is the highest in these bands and the emissivity maximum of the objects at T≈300 K is at the wavelength λ≈10 μm), though in recent years there has been increasing interest in longer wavelengths stimulated by space applications.

Progress

General theory of photon detectors

The photodetector is a slab of homogeneous semiconductor with the actual “electrical” area, A_e, that is coupled to a beam of infrared radiation by its optical area, A_o (Fig. 3). Usually, the optical and electrical areas of the device are the same or close. The use of optical concentrators can increase the A_o/A_e ratio.

The current responsivity of the photodetector is determined by the quantum efficiency, η, and by the photoelectric gain, g. The quantum efficiency value describes how well the

General theory of thermal detectors

Thermal detectors operate on a simple principle, that when heated by incoming IR radiation their temperature increases and the temperature changes are measured by any temperature-dependent mechanism, such as thermoelectric voltage, resistance, pyroelectric voltage. The simplest representation of the thermal detector is shown in Fig. 10. The detector is represented by the thermal capacitance C_th coupled via the thermal conductance G_th to a heat sink at the constant temperature T. In the absence

Comparison of fundamental limits of photon and thermal detectors

The temperature dependence of the fundamental limits of $D^{∗}$ of photon and thermal detectors for different levels of background are shown in Fig. 11, Fig. 12.

It results from Fig. 11 that in LWIR spectral range, the performance of intrinsic IR detectors (HgCdTe photodiodes) is higher than for other types of photon detectors. HgCdTe photodiodes with background limited performance operate at temperature below ≈80 K. HgCdTe is characterized by high optical absorption coefficient and quantum efficiency

Focal plane arrays

There are many important military and civilian applications of IR FPAs, which are frequently called “dual technology applications.” Lately, one should point out the growing utilisation of IR technologies in the civilian sphere at the expense of new materials and technologies and also the noticeable price decrease in these high cost technologies. Demands to use these technologies are quickly growing due to their effective applications, e.g., in global monitoring of environmental pollution and

Photon detectors

The increased sensitivity, resolution in system complexity of FPAs offer significant advantages in military as well as civilian applications in thermal imaging, guidance, reconnaissance, surveillance, ranging and communication systems. From fundamental considerations HgCdTe is the most important semiconductor alloy system for IR detectors in the spectral range between 1 and 25 μm. HgCdTe detectors as the intrinsic photon detectors absorb the IR radiation across the fundamental energy gap and are

Thermal detectors

The use of thermal detectors for IR imaging has been the subject of research and development for many decades. Thermal detectors are not useful for high-speed scanning thermal imagers. Only pyroelectric vidicons have found more widespread use. These devices achieved their fundamental limits of performance by about 1970. However, the speed of thermal detectors is quite adequate for non-scanned imagers with 2-D detectors. Fig. 72 shows the dependence of NEDT on noise bandwith for typical

Conclusions

The intention of this paper has been to present state-of-the-art both photon and thermal detectors, with emphasis on the material properties, device structure, and their impact on FPA performance, especially in LWIR and VLWIR spectral regions.

At present, HgCdTe is widely used variable gap semiconductor and has a privilege position both in LWIR as well as VLWIR spectral ranges. Fig. 85 shows a plot of the thermal detectivity (300 K, 0° FOV) versus operating temperature for the most prominent

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ReviewInfrared detectors: status and trends

Abstract

Introduction

Section snippets

Historical aspects of modern infrared technology

Classification of infrared detectors

General theory of photon detectors

General theory of thermal detectors

Comparison of fundamental limits of photon and thermal detectors

Focal plane arrays

Photon detectors

Thermal detectors

Conclusions

Infrared Physics

Journal of Physics and Chemistry of Solids

Infrared Physics

Progress in Quantum Electronics

Infrared Physics

Infrared Physics Technology

Sensors and Actuators A

Infrared Physics Technology

Infared Phys. Technol.

Infrared Physics

Journal of Crystal Growth

Journal of Crystal Growth

Experiments on the refrangibility of the invisible rays of the Sun

Philosophical Transaction on Royal Society of London

The Detection and Measurement of Infrared Radiation

Elements of Infrared Technology

Historical survey of the early development of the infrared spectral region

American Journal of Physics

The infrared pioneers—II. Macedonio Melloni

Infrared Physics

Notes on the change of resistance of certain substrates in light

Physics Reviews

Film-type infrared photoconductors

Proceedings of IRE

Infrared detectors in the next millennium

Proceedings of SPIE

Infrared Detectors

Charge-coupled semiconductor devices

Bell Syst. Tech. J.

Single-crystal lead-tin chalcogenides

A pneumatic infrared detector

Review of Scientific Instruments

Properties of thermistor infrared detectors

Journal of Optics Society of America

Thermal imaging by means of the evaporograph

Applied Optics

The pyroelectric vidicon—A review

Proceedings of SPIE

Monolithic silicon microbolometer arrays

Uncooled IR focal plane arrays

Opto-Electronics Review

Uncooled microbolometer infrared sensor arrays

Pyroelectric materials and devices

Uncooled Thermal Imaging. Arrays, Systems, and Applications

Concepts in Photoconductivity and Allied Problems

Quantum-well infrared photodetectors

Journal of Applied Physics

Radiative lifetime in semiconductors for infrared detection

Infrared Physics

Elements of Infrared Technology

The photon detection process

The Detection and Measurement of Infrared Radiation

Performance limitations of photon and thermal infrared detectors

Opto-Electronics Review

Infrared focal plane array technology

Proceedings of IEEE

Recent advances in staring hybrid focal plane arrayscomparison of HgCdTe, InGaAs, and GaAs/AlGaAs detector technologies

Proceedings of SPIE

Photovoltaic CdHgTe-silicon hybrid focal planes

Proceedings of SPIE

Status of infrared detectors

Proceedings of SPIE

2048×2048 HgCdTe focal plane arrays for astronomy applications

Proceedings of SPIE

Ultra-low noise infrared focal plane array status

Proceedings of SPIE

Review
Infrared detectors: status and trends