No description available.

InAsxSb1-x (Indium Arsenide Antimonide) is an important low bandgap semiconductor whose high quality growth on GaAs or Si substrates is indispensible for low cost, large format infrared focal plane arrays (FPAs). Quantum well infrared photodetector (QWIP) technology, relying on mature semiconductors, is also promising for the above purpose. While AlGaAs/GaAs has been the standard material system for QWIPs, the search for alternative materials is needed for better performance. This thesis reports a detailed investigation of molecular beam epitaxy grown mid-wavelength infrared InAsxSb1-x photodiodes on alternative substrates, and long wavelength infrared InP/InGaAs QWIPs. In the first part of the study, InSb and InAs0.8Sb0.2 photodiodes grown on Si and GaAs substrates are investigated to reveal the performance degrading mechanisms due to large lattice mismatch. InAs0.8Sb0.2/GaAs photodiodes yield peak detectivities of 1.4&times / 1010 and 7.5&times / 108 cmHz&frac12 / /W at 77 K and 240 K, respectively, showing that the alloy is promising for both cooled and near room temperature detectors. Under moderate reverse bias, 80 K RoA product limiting mechanism is trap assisted tunneling, which introduces considerable 1/f noise. InSb/Si photodiodes display peak 77 K detectivity as high as ~1&times / 1010 cmHz 1/2/W and reasonably high peak quantum efficiency in spite of large lattice mismatch. RoA product of detectors at 80 K is limited by Ohmic leakage with small activation energy (25 meV). Bias and temperature dependence of 1/f noise is in reasonable agreement with Kleinpenning&rsquo / s mobility fluctuation model, confirming the validity of this approach. The second part of the study concentrates on InP/In0.53Ga0.47As QWIPs, and 640&times / 512 FPA, which to our knowledge, is the largest format InP/InGaAs QWIP FPA reported. InP/InGaAs QWIPs yield quantum efficiency-gain product as high as 0.46 under moderate bias. At 70 K, detector performance is background limited with f/2 aperture up to ~3 V bias where peak responsivity (2.9 A/W) is thirty times higher than that of the Al0.275Ga0.725As/GaAs QWIP with similar spectral response. Impact ionization in InP/InGaAs QWIPs does not start until the average electric-field reaches 25 kV/cm, maintaining high detectivity under moderate bias. The 640&times / 512 InP/InGaAs QWIP FPA yields noise equivalent temperature difference of ~40 mK at an FPA temperature as high as 77 K and reasonably low NETD even with short integration times (t). 70 K NETD values of the FPA with f/1.5 optics are 36 and 64 mK under &ndash / 0.5 V (t=11 ms) and &ndash / 2 V (t=650 Rs) bias, respectively. The results clearly show the potential of InP/InGaAs QWIPs for thermal imaging applications requiring short integration times. Keywords: Cooled infrared detectors, InAsSb, QWIP, focal plane array.

"December, 2003" / Includes bibliographical references (p. 311-348) / Accompanying CD-ROM entitled: 'SPM_PhD_Thesis' contains MATLAB_Algorithms (algorithms for T-ray data analysis and display, as described in the Thesis); Appendix D (Example_Raw_Data_Files - examples of raw T-ray data files, used by the MATLAB algorithms in MATLAB_Algorithms); and Thesis_PDF (a copy of the Thesis printed in Adobe's Portable Document Format (PDF)). / System requirements for accompanying CD-ROM: CD-ROM drive ; Adobe Acrobat reader ; Matlab software. / xxxiv, 358 p. : ill. (col.) ; 30 cm. + 1 CD-ROM (col. ill. ; 4 3/4 in.) / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Electrical and Electronic Engineering, 2004

[Truncated abstract] HgCdTe is the leading semiconductor material for the fabrication of high performance infrared photon detectors, in particular, for detection of radiation beyond the near infrared. State-of-the-art infrared detection and imaging systems are currently based around high density focal plane arrays consisting of HgCdTe photodiodes as detector elements. Despite the high performance of HgCdTe infrared detectors, and the many benefits they can offer to industry and society, their utilisation remains limited due to the high cost of production. The chemical composition and narrow bandgap of the HgCdTe material used for infrared detection means that the material is inherently very susceptible to defect formation caused by the processing procedures required for device fabrication. Consequently, fabrication of HgCdTe photodiode arrays have traditionally been characterised by low yields and high costs for arrays that meet required operability specifications. In this thesis a new photodiode fabrication technology with the potential to improve device yields over traditional fabrication technologies is presented. This new fabrication technology is distinguished from others by the use of plasma-induced p-to-n type conversion of HgCdTe for junction formation. This allows great simplification of the fabrication process and avoids high temperature processing during and after junction formation, and keeps the junction protected from the atmosphere at all stages of fabrication. The development of the photodiode fabrication technology using plasma-induced junction formation has involved characterising the electrical transport properties of the type-converted layers, fabrication and characterisation of photodiodes, and photodiode dark current modelling

Thesis (Ph.D.)--University of Adelaide, School of Electrical and Electronic Engineering, 2004. / "December, 2003" Includes bibliographical references (p. 311-348).

Thesis (Ph.D.)--University of Adelaide, School of Electrical and Electronic Engineering, 2005. / Includes bibliographical references (p. 349-379) and index.

abstract: Photodetectors in the 1.7 to 4.0 μm range are being commercially developed on InP substrates to meet the needs of longer wavelength applications such as thermal and medical sensing. Currently, these devices utilize high indium content metamorphic Ga1-xInxAs (x > 0.53) layers to extend the wavelength range beyond the 1.7 μm achievable using lattice matched GaInAs. The large lattice mismatch required to reach the extended wavelengths results in photodetector materials that contain a large number of misfit dislocations. The low quality of these materials results in a large nonradiative Shockley Read Hall generation/recombination rate that is manifested as an undesirable large thermal noise level in these photodetectors. This work focuses on utilizing the different band structure engineering methods to design more efficient devices on InP substrates. One prospective way to improve photodetector performance at the extended wavelengths is to utilize lattice matched GaInAs/GaAsSb structures that have a type-II band alignment, where the ground state transition energy of the superlattice is smaller than the bandgap of either constituent material. Over the extended wavelength range of 2 to 3 μm this superlattice structure has an optimal period thickness of 3.4 to 5.2 nm and a wavefunction overlap of 0.8 to 0.4, respectively. In using a type-II superlattice to extend the cutoff wavelength there is a tradeoff between the wavelength reached and the electron-hole wavefunction overlap realized, and hence absorption coefficient achieved. This tradeoff and the subsequent reduction in performance can be overcome by two methods: adding bismuth to this type-II material system; applying strain on both layers in the system to attain strain-balanced condition. These allow the valance band alignment and hence the wavefunction overlap to be tuned independently of the wavelength cutoff. Adding 3% bismuth to the GaInAs constituent material, the resulting lattice matched Ga0.516In0.484As0.970Bi0.030/GaAs0.511Sb0.489superlattice realizes a 50% larger absorption coefficient. While as, similar results can be achieved with strain-balanced condition with strain limited to 1.9% on either layer. The optimal design rules derived from the different possibilities make it feasible to extract superlattice period thickness with the best absorption coefficient for any cutoff wavelength in the range.   / Dissertation/Thesis / M.S. Electrical Engineering 2013

This study focuses on the development of InAs/GaInSb strained-layer superlattice structures by metal organic chemical vapour deposition (MOCVD), and deals with two aspects of the development of InAs/GaInSb SLS’s by MOCVD viz. the deposition of nano-scale (~100 Å) GaInSb layers, and the electrical characterization of unstrained InAs. The first part of this work aims to study the MOCVD growth of GaInSb layers in terms of deposition rate and indium incorporation on the nano-scale. This task is approached by first optimizing the growth of relatively thick (~2 μm) epitaxial films, and then assuming similar growth parameters during nano-scale deposition. The GaInSb layers were grown as part of GaInSb/GaSb quantum well (QW) structures. By using this approach, the GaInSb QW’s (~100 Å) could be characterized with the use of photoluminescence spectroscopy, which, when used in conjunction with transmission electron microscopy and/or X-ray diffractomery, proves useful in the analysis of such small scale deposition. It is shown that the growth rate of GaInSb on the nano-scale approaches the nominal growth rates determined from thick (~2 μm) GaInSb calibration layers. The In incorporation efficiency in nano-layers, however, was markedly lower than what was predicted by the GaInSb calibration layers. This reduction in indium incorporation could be the result of the effects of strain on In incorporation. The choice of substrate orientation for QW deposition was also studied. QW structures were grown simultaneously on both (100) and 2°off (100) GaSb(Te) substrates, and it is shown that growth on non-vicinal substrates is more conducive to the deposition of high quality QW structures. The second part of this study focuses on the electrical characterization of unstrained InAs. It is long known that conventional Hall measurements cannot be used to accurately characterize InAs epitaxial layers, as a result of parallel conduction resulting from surface and/or interface effects. This study looks at extracting the surface and bulk electrical properties of n-type InAs thin films directly from variable magnetic field Hall measurements. For p-type InAs, the situation is complicated by the relatively large electron to hole mobility ratio of InAs which tends to conceal the p-type nature of InAs thin films from Hall measurements. Here, this effect is illustrated by way of theoretical simulation of Hall data.

Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1979 / Includes bibliographical references. / by Leslie Louis Szepesi, Jr. / M.S. / M.S. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

Detectors sensitive to thermal and reflected infrared radiation are widely used for night-vision, communications, thermography, and object tracking among other military, industrial, and commercial applications. System requirements for the next generation of ultra-high-performance infrared detectors call for increased functionality such as large formats (> 4K HD) with wide field-of-view, multispectral sensitivity, and on-chip processing. Due to the low yield of infrared material processing, the development of these next-generation technologies has become prohibitively costly and time consuming. In this work, it will be shown that physics-based numerical models can be applied to predictively simulate infrared detector arrays of current technological interest. The models can be used to a priori estimate detector characteristics, intelligently design detector architectures, and assist in the analysis and interpretation of existing systems. This dissertation develops a multi-scale simulation model which evaluates the physics of infrared systems from the atomic (material properties and electronic structure) to systems level (modulation transfer function, dense array effects). The framework is used to determine the electronic structure of several infrared materials, optimize the design of a two-color back-to-back HgCdTe photodiode, investigate a predicted failure mechanism for next-generation arrays, and predict the systems-level measurables of a number of detector architectures.