Design and characteristics of high performance mid-wavelength type-2 superlattice sensors

2018
Oğuz, Fikri
Type-II Superlattices (T2SLs) are bandgap engineered structures that have attracted a lot of attention in the last couple of decades and is still some of the hot topics in infrared imaging applications. T2SLs are the most promising member of the quantum structured infrared family. By the end of maturity period of T2SLs, Focal Plane Array (FPA) level products have been released since a decade. Offering performance compatible with high-end infrared systems, yielding respectable results and still being open to further development make T2SL subjects worth to work on. The flexibility in design and the opportunity provided by nature of structures enable researchers and manufacturers to give their focus on this today’s world materials system. This thesis work covers the state of the art Mid-Wavelength Infrared Region (MWIR) InAs/GaSb Type-II Superlattice infrared technology in terms of design, fabrication, and characterization. Large format (640 x 512) and small pitch (15 µm) architecture are implemented for the fabrication of T2SL FPAs. The critical design parameters and design approaches for ultimate performance and reasons for capabilities of T2SLs to offer such performance are handled. After the presentation of detailed fabrication procedure and experimented fabrication methods, large area pixel level and FPA level characterizations are also discussed. The performance comparisons of experimented fabrication processes are demonstrated. With dark current modeling of large area T2SL diodes, the dominant dark current mechanisms for varying bias regions are clarified. With this modeling, our properly designed T2SL structure shows no tunneling dark current and is dominated only by detector shunt current at most of the bias regions. Electro-optical measurements yielded very satisfactory results. The optimized FPA which is a 15 µm pitch detector with cut-off wavelength of 4.92 µm yields 1.2 A⁄W peak responsivity and 30 mK Noise Equivalent Temperature Difference (NETD) with f⁄2.3 optics. The calculated quantum efficiency for this detector is larger than 60 %. Example images were acquired using optimized FPA device, and are provided in the thesis for demonstrative purposes.

Suggestions

Design and implementation of high fill factor structures on low-cost uncooled infrared sensors
Ertürk, Ozan; Akın, Tayfun; Department of Electrical and Electronics Engineering (2015)
This thesis presents the design and implementation steps of high fill factor structures for existing SOI diode low-cost microbolometer FPAs. Advancements in uncooled infrared detectors enable high performance military grade uncooled microbolometers as well as ultra-low-cost infrared imagers for civilian applications. The trend in uncooled microbolometers to reduce the pixel pitch has become increasingly significant to lower the cost of detector and system integration due to optics, and increase spatial reso...
Development of high fill factor and high performance uncooled infrared detector pixels
Küçük, Şeniz Esra; Akın, Tayfun; Department of Electrical and Electronics Engineering (2011)
This thesis presents the design, fabrication and characterization of high performance and high fill factor surface micromachined uncooled infrared resistive microbolometer detectors which can be used in large format focal plane arrays (FPAs). The detector pixels, which have a pixel pitch of 25 μm, are designed and fabricated as two-level structures using the enhanced sandwich type resistor while the active material is selected as Yttrium Barium Copper Oxide (YBCO). First level of the pixel structure is allo...
Development and characterization of low-cost uncooled infrared sensors for commercial applications
Tankut, Firat; Akın, Tayfun; Eminoğlu, Selim; Department of Electrical and Electronics Engineering (2013)
This thesis reports the study on the development and characterization of low-cost uncooled microbolometer type infrared detectors, which are fabricated using standard CMOS and MEMS processes. Characterization of the detectors is the first step of developing infrared sensors with better performance. The characterized pixel has a 70 μm pitch and includes 4 serially connected diodes as the detector circuit. Thermal conductance (Gth), temperature sensitivity (TC) and, optical absorption are measured in scope of...
Development of high performance uncooled infrared detector materials
Kebapçı, Başak; Akın, Tayfun; Turan, Raşit; Department of Micro and Nanotechnology (2011)
This thesis reports both the optimizations of the vanadium oxide (VOx) thin film as an active infrared detector material by the magnetron sputtering deposition method and its use during fabrication of proper resistors for the microbolometers. Vanadium oxide is a preferred material for microbolometers, as it provides high TCR value, low noise, and reasonable resistance, and a number of high-tech companies have used this material to obtain state-of-the-art microbolometer arrays. This material is first used in...
Design and implementation of a single slope adc for digital output cooled infrared readout integrated circuits
Akyürek, Fatih; Bayram, Barış; Department of Electrical and Electronics Engineering (2016)
Readout Integrated Circuits (ROIC) have been commonly implemented with analog video output buffers throughout history. Image signals are converted into digital by an external ADC card, which is placed outside the Dewar. Although analog output method is easier to implement, it is susceptible to the environmental noise due to the non-differential output. Moreover, the ADC proximity card placed outside of the dewar contributes to the system complexity. This thesis presents the design of a single slope ADC dedi...
Citation Formats
F. Oğuz, “Design and characteristics of high performance mid-wavelength type-2 superlattice sensors,” M.S. - Master of Science, Middle East Technical University, 2018.