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Infrared detectors: status and trends

The physical properties of detectors based on intraband optical absorption in quantum dots is described and examined in the interest of providing a competitive alternative infrared (IR) detector technology. These quantum dot detectors are an extension of quantum well infrared photodetectors and are expected to have a large performance advantage. A model is developed for quantum dot infrared photodetectors based on fundamental performance limitations enabling a direct comparison between IR materials technologies. A comparison is made among HgCdTe, quantum well, and quantum dot IR detectors, where quantum dots are expected to have the potential to outperform quantum wells by several orders of magnitude and compete with HgCdTe. In this analysis, quantum dots are expected to possess the fundamental ability to achieve the highest IR detector performance if quantum dot arrays with high size uniformity and optimal bandstructure may be achieved.

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Evaluation of the fundamental properties of quantum dot infrared detectors

The first decade of the 21st-century has seen a rapid development in infrared photodetector technology. At the end of the last millennium there were two dominant IR systems, InSb- and HgCdTe-based detectors, which were well developed and available in commercial systems. While these two systems saw improvements over the last twelve years, their change has not nearly been as marked as that of the quantum-based detectors (i.e., QWIPs, QDIPs, DWELL-IPs, and SLS-based photodetectors). In this paper, we review the progress made in all of these systems over the last decade plus, compare the relative merits of the systems as they stand now, and discuss where some of the leading research groups in these fields are going to take these technologies in the years to come.

Progress in Infrared Photodetectors Since 2000

We report the most recent work on the modeling of type-II InAs/GaSb superlattices using the empirical tight binding method in an ${\mathrm{sp}}^{3}{s}^{*}$ basis. After taking into account the antimony segregation in the InAs layers, the modeling accuracy of the band gap has been improved. Our calculations agree with our experimental results within a certain growth uncertainty. In addition, we introduce the concept of ${\mathrm{Ga}}_{x}{\mathrm{In}}_{1\ensuremath{-}x}$ type interface engineering in order to reduce the lattice mismatch between the superlattice and the GaSb (001) substrate to improve the overall superlattice material quality.

Modeling of type-II InAs/GaSb superlattices using an empirical tight-binding method and interface engineering

We report the most recent advance in the area of type II InAs/GaSb superlattice photovoltaic detectors that have cutoff wavelengths beyond 25 μm, with some at nearly 32 μm. The photodiodes with a heterosuperlattice junction showed Johnson noise limited peak detectivity of 1.05×1010 cm Hz1/2/W at 15 μm under zero bias, and peak responsivity of 3 A/W under −40 mV reverse bias at 34 K illuminated by ∼300 K background with a 2π field-of-view. The maximum operating temperature of these detectors ranges from 50 to 65 K. No detectable change in the blackbody response has been observed after 5–6 thermal cyclings, with temperature varying between 15 and 296 K in vacuum.

Type II InAs/GaSb superlattice photovoltaic detectors with cutoff wavelength approaching 32 μm

We report on the demonstration of high-performance p-i-n photodiodes based on type-II InAs/GaSb superlattices with 50% cut-off wavelength λc=16 μm operating at 80 K. Material is grown by molecular beam epitaxy on GaSb substrates with excellent crystal quality as evidenced by x-ray diffraction and atomic force microscopy. The processed devices show a current responsivity of 3.5 A/W at 80 K leading to a detectivity of ∼1.51×1010 cmHz1/2/W. The quantum efficiency of these devices is about 35% which is comparable to HgCdTe detectors with a similar active layer thickness.

High-performance InAs/GaSb superlattice photodiodes for the very long wavelength infrared range

We report a demonstration of very long wavelength infrared detectors based on InAs/GaSb superlattices operating at T=80 K. Detector structures with excellent material quality were grown on an optimized GaSb buffer layer on GaAs semi-insulating substrates. Photoconductive devices with 50% cutoff wavelength of λc=17 μm showed a peak responsivity of about 100 mA/W at T=80 K. Devices with 50% cutoff wavelengths up to λc=22 μm were demonstrated at this temperature. Good uniformity was obtained over large areas even for the devices with very long cutoff wavelengths.

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Very long wavelength infrared type-II detectors operating at 80 K

Development of quantum well infrared photodetectors at the center for quantum devices

The world at the end of the 20th Century has become blue. Indeed, this past decade has witnessed a blue rush towards the development of violet-blue-green light emitting diodes (LEDs) and laser diodes (LDs) based on wide band gap III-nitride semiconductors. And the hard work has culminated with, first, the demonstration of commercial high brightness blue and green LEDs and of commercial violet LDs, at the very end of this decade. Thanks to their extraordinary properties, these semiconductor materials have generated a plethora of activity in semiconductor science and technology. Novel approaches are explored daily to improve the current optoelectronics state-of- the-art. Such improvements will extend the usage and the efficiency of new light sources (e.g. white LEDs), support the rising information technology age (e.g. high density optical data storage), and enhance the environmental awareness capabilities of humans (ultraviolet and visible photon detectors and sensors). Such opportunities and many others will be reviewed in this presentation.

Yoon-Soo Park

Papers

High-performance InAs/GaSb superlattice photodiodes for the very long wavelength infrared range

Very long wavelength infrared type-II detectors operating at 80 K

Development of quantum well infrared photodetectors at the center for quantum devices

Wide bandgap III-Nitride semiconductors : opportunities for future optoelectronics

Wide-bandgap III-nitride semiconductors: opportunities for future optoelectronics