New material systems for third generation infrared photodetectors

Rogalski, Antoni

doi:10.2478/s11772-008-0047-7

Cited by 83 publications

(46 citation statements)

References 125 publications

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“…This offers the possibility of directly controlling the electron-hole wave-function overlap and gives rise to an intermediate carrier localization regime in which one carrier is confined in one of the heteroNC components while the other is delocalized over both materials. 1,2,4 This flexibility in tailoring the optoelectronic properties of the heteronanostructure has important consequences for a number of technologies, and opens up interesting application possibilities: miniaturized low-threshold lasers, 2 photovoltaic devices, 5 fast optical switches, 6 systems for quantum information processing, 7 advanced IR detectors, 8 fast access memories, 9 spintronic devices, 10 and labels for biomedical imaging 11 and optical "nanoscopy" ͑i.e., super-resolution optical microscopy based on stimulated emission depletion 12 ͒. The realization of this wide range of potential applications requires a strict control over the fabrication of the heteronanostructures and a thorough understanding of their properties.…”

Section: Introductionmentioning

confidence: 99%

“…1,[6][7][8][9][10]13,14 However, the energetic barriers in these nanostructures are usually lower than those attainable in colloidal QDs and heteroNCs, which are typically much smaller than their MBE counterparts. Moreover, colloidal chemistry methods are cheaper and easier to upscale than MBE techniques, and offer the additional advantages of processability and easier control over size, shape, and surface.…”

Section: Introductionmentioning

confidence: 99%

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Formation of nanoscale spatially indirect excitons: Evolution of the type-II optical character of CdTe/CdSe heteronanocrystals

Donegá

2010

Phys. Rev. B

107

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In this work, the evolution of the optical properties of nanoscale spatially indirect excitons as a function of the size, shape, and composition of the heteronanostructure is investigated, using colloidal CdTe/CdSe heteronanocrystals ͑2.6 nm diameter CdTe core and increasing CdSe volume fraction͒ as a model system. Emphasis is given to quantitative aspects such as the absorption cross section of the lowest-energy exciton transition ͑ SS ͒, Stokes shift, linewidths, and the exciton radiative lifetime. The hole wave function remains confined to the CdTe core while the electron wave function is initially delocalized over the whole heteronanocrystal ͑type-I 1/2 regime͒, and gradually localizes in the CdSe segment as the growth proceeds, until the spatially indirect exciton transition becomes the lowest-energy transition ͑type-II regime͒. This results in a progressive shift of the optical transitions to lower energies, accompanied by a decrease in the oscillator strengths at emission energies and an increase in the exciton radiative lifetimes. The onset of the type-II regime is characterized by the loss of structure of the lowest-energy absorption band, accompanied by a simultaneous increase in the Stokes shift values and transition linewidths. This can be understood by considering the dispersion of the hole and electron states in k space. The SS values decrease rapidly in the type-I 1/2 regime but only slightly in the type-II regime. This shows that the indirect exciton formation leads primarily to redistribution of the oscillator strength of the lowest-energy transition over a wider frequency range. The total absorption cross section per ion-pair unit ͑i.e., integrated over all the exciton transitions͒ remains essentially constant during the heteronanocrystal growth, demonstrating that SS is redistributed from higher-energy transitions of both the CdTe and the CdSe segments, in response to the reduction in the electron-hole wavefunction overlap. Two radiative decay rates are observed and ascribed to exciton states with different degrees of localization of the electron wave function ͑an upper state with a faster decay rate and a lower state with a slower decay rate͒. The results presented here provide fundamental insights into nanoscale spatially indirect exciton transitions, highlighting the crucial role of a number of parameters ͑viz., electron-hole spatial correlation, exciton dispersion and exciton degeneracy, shape effects, and electronic coupling͒.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Formation of nanoscale spatially indirect excitons: Evolution of the type-II optical character of CdTe/CdSe heteronanocrystals

Donegá

2010

Phys. Rev. B

107

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“…Recently, type−II InAs/GaInSb SLs has emerged as a candidate for third generation IR detectors [108]. Over the past few years type−II superlattice based detectors have been also made rapid progress in fabrication of dual−band FPAs.…”

Section: Cooled Fpasmentioning

confidence: 99%

History of infrared detectors

Rogalski

2012

Opto-Electronics Review

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411

207

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This paper overviews the history of infrared detector materials starting with Herschel’s experiment with thermometer on February 11th, 1800. Infrared detectors are in general used to detect, image, and measure patterns of the thermal heat radiation which all objects emit. At the beginning, their development was connected with thermal detectors, such as thermocouples and bolometers, which are still used today and which are generally sensitive to all infrared wavelengths and operate at room temperature. The second kind of detectors, called the photon detectors, was mainly developed during the 20th Century to improve sensitivity and response time. These detectors have been extensively developed since the 1940’s. Lead sulphide (PbS) was the first practical IR detector with sensitivity to infrared wavelengths up to ∼3 μm. After World War II infrared detector technology development was and continues to be primarily driven by military applications. Discovery of variable band gap HgCdTe ternary alloy by Lawson and co-workers in 1959 opened a new area in IR detector technology and has provided an unprecedented degree of freedom in infrared detector design. Many of these advances were transferred to IR astronomy from Departments of Defence research. Later on civilian applications of infrared technology are frequently called “dual-use technology applications.” One should point out the growing utilisation of IR technologies in the civilian sphere based on the use of new materials and technologies, as well as the noticeable price decrease in these high cost technologies. In the last four decades different types of detectors are combined with electronic readouts to make detector focal plane arrays (FPAs). Development in FPA technology has revolutionized infrared imaging. Progress in integrated circuit design and fabrication techniques has resulted in continued rapid growth in the size and performance of these solid state arrays.

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“…Simultaneously, requirements to s(V th ) and s(x) more strict than those adopted in the calculations illustrated by Fig. 7 go beyond the state−of−the−art technology limit in terms of dispersions s(V th ) and s(x) presently achievable both in silicon CMOS technology and in the epitaxial tech− nology of Hg 1-x Cd x Te layers [1,21,22].…”

Section: Calculated Characteristics Of Ir Fpasmentioning

confidence: 99%