ASELSAN, the largest defense company in Turkey, develops high performance electro-optical systems for various applications. Due to the technical challenges and relatively higher cost associated with MCT technology, there is a search for an alternative material system all over the world, especially for the applications that need relatively low quantum efficiency and high volume production. Research and development activities have been carried out on developing InAs/GaSb T2SL detectors for mid-wavelength infrared (MWIR) technology in ASELSAN. In this paper, recent results for 15μm pitch MWIR T2SL and 10μm pitch MWIR T2SL detectors are presented. InAs/GaSb T2SL epilayers are used for FPA fabrication with mesa pixel structures. Typically, over 99% operability and less than 25 mK NETD values are achieved for 15 μm pitch 640x512 format MWIR T2SL FPAs at IDDCA level (F/4). Besides ongoing efforts on development of FPAs with 15 μm pixel pitch, development activities for pixel pitch reduction are also initiated recently for MWIR T2SL FPAs for improving resolution and promising results are achieved. For this purpose, MWIR T2SL FPAs with 1280x1024/10μm resolution/pixel pitch are fabricated and NETD values less than 25 mK (F/2) with pixel operability of 97% are achieved for the first prototypes.
ASELSAN, the largest defense company in Türkiye, develops high performance electro-optical systems for various applications. Research and development activities have been carried out on developing HgCdTe (MCT) detectors for long-wavelength infrared (LWIR) and mid-wavelength infrared (MWIR). In this paper, recent results for VGA 15μm pitch MWIR MCT detectors at IDDCA level are presented. P-on-n MCT epilayers are used for FPA fabrication with either mesa or planar pixel structures. Typically, over 99% operability and less than 20mK NETD values are achieved for 15μm pitch 640x512 format MWIR MCT FPAs at IDDCA level (F/4) in a repeatable fashion. Thermal cycle, mechanical shock, vibration and environmental tests (such as storage and operation under hot and cold temperatures) were applied to these MWIR MCT IDDCAs and passed successfully. Besides ongoing efforts on development of FPAs with 15μm pixel pitch, development activities for pixel pitch reduction also initiated recently for MWIR MCT and very promising results are achieved.
Recent advances in short-wave infrared (SWIR) technology including numerous new applications in civil areas, fusion with visible wavelengths, and integration with active imaging systems triggered the SWIR photodetector research at ASELSAN for both passive and active imaging. SWIR focal plane arrays with a 640x512 format and 15μm pitch were developed and coupled with ASEL64015C readout circuits which had been designed at ASELSAN as well. Through extensive research and development dark current density values <10 nA/cm2 (at 20°C) and operabilities >;99% were achieved. This paper reviews the work that has been conducted on SWIR detector development at ASELSAN.
Many microelectronic devices require bonding dissimilar materials to operate under extreme operating conditions. Furthermore, certain applications, such as cooled infrared (IR) detection, require large temperature cycles between ambient and cryogenic temperatures under ultra-high vacuum (UHV) conditions. The complex expansion and contraction of the various materials within the detector package structure during temperature cycles introduces significant internal stresses that may ultimately result in the failure of the sensor and/or the package. Added to this complexity is the process sensitivity of the fabricated device to elevated temperatures and adhesive application. With orders-ofmagnitude difference between gap sizes, adhesive properties such as viscosity, cure kinetics, and process temperatures become paramount for successful sensor integration. In addition, stringent outgassing requirements associated with ultra-high vacuum application further complicates the selection process for cryogenic adhesives. Under these constraints, a myriad of commercial epoxy adhesives were evaluated. We devised a characterization methodology using a combination of various analytical techniques which elucidated the complex flow properties, and cure kinetics while highlighting critical characteristics necessary for a successful material for this application with a focus on rapid cycles of learning. As the application space matures, we see the need for a next generation of adhesives for demanding and ubiquitous infrared sensing applications.
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