2D Focal Plane Array Research Articles

Mesa-structures and Focal Plane Arrays based on epitaxially grown InSb layers

Aspects of epitaxially grown indium antimonide (InSb) on InSb substrates (InSb-on-InSb) by molecular beam epitaxy (MBE) for the 2D focal plane arrays fabrication process have been described. The epitaxial growth offers possibility for complex structure production, and then such structures suppose more effective control of the thermal generation charge carriers as the detector temperature is raised above 80 K. Investigations of mid-wave infrared (MWIR) 320256 FPAs with 30 μm pitch and 640512 FPAs with 15 μm pitch based on 
 InSb-on-InSb layers have shown high performance: the average detectivity at T = 77 K more than 21011 cmW-1Hz1/2, the average value of noise equivalent temperature difference 
 (NETD) with a cold aperture of 60o at T = 77K was in the range of 10–20 mK. High quality thermal imaging images were obtained in real time mode.

Robust, Sensitive, and Inexpensive 2D Focal Plane Array Upconverting MMW Imaging Into the Visible

A new concept of millimeter-wave (MMW) imaging system is demonstrated in this letter. The new concept is based on glow discharge detector (GDD) focal plane array (FPA) and a basic CMOS camera. The GDD elements emit optical light as a function of the incident MMW radiation intensity. By synchronizing the modulation of the MMW source with the exposure time of the CMOS camera in a way that every two consecutive frames were captured with the influence of the MMW radiation and without it, we were able to observe the effect of the MMW radiation alone on the GDD FPA without the light deriving from the GDD DC bias.

High-dynamic range compressive spectral imaging by grayscale coded aperture adaptive filtering

<p class="p1">The coded aperture snapshot spectral imaging system (CASSI) is an imaging architecture which senses the three dimensional informa-tion of a scene with two dimensional (2D) focal plane array (FPA) coded projection measurements. A reconstruction algorithm takes advantage of the compressive measurements sparsity to recover the underlying 3D data cube. Traditionally, CASSI uses block-un-block coded apertures (BCA) to spatially modulate the light. In CASSI the quality of the reconstructed images depends on the design of these coded apertures and the FPA dynamic range. This work presents a new CASSI architecture based on grayscaled coded apertu-res (GCA) which reduce the FPA saturation and increase the dynamic range of the reconstructed images. The set of GCA is calculated in a real-time adaptive manner exploiting the information from the FPA compressive measurements. Extensive simulations show the attained improvement in the quality of the reconstructed images when GCA are employed. In addition, a comparison between traditional coded apertures and GCA is realized with respect to noise tolerance.</p>

Design of Current-Type Readout Integrated Circuit for 160 × 120 Pixel Array Applications

We propose a Readout Integrated Circuit (ROIC), which applies a fixed current bias sensing method to the input stage in order to simplify the circuit structure and the infrared sensor characteristic control. For the sample-and-hold stage to display and control a signal detected by the infrared sensor using a two-dimensional (2D) focal plane array, a differential delta sampling (DDS) circuit is proposed, which effectively removes the FPN. In addition, the output characteristic is improved to have wider bandwidth and higher gain by applying a two-stage variable gain amplifier (VGA). The output characteristic of the proposed device was 23.91 ㎷/℃, and the linearity error rate was less than 0.22%. After checking the performance of the ROIC using HSPICE simulation, the chip was manufactured and measured using the SMIC 0.35 ㎛ standard CMOS process to confirm that the simulation results from the actual design are in good agreement with the measurement results.

Megapixel digital InSb detector for midwave infrared imaging

Since the late 1990s Semiconductor devices (SCDs) has developed and manufactured a variety of InSb two-dimensional (2D) focal plane arrays (FPAs) that were implemented in many infrared (IR) systems and applications. SCD routinely manufactures both analog and digital InSb FPAs with array formats of 320×256, 480×384, and 640×512 elements, and pitch size in the range 15 to 30 μm. These FPAs are available in many packaging configurations, including fully integrated detector-Dewarcooler-assembly, with either closed-cycle Stirling or open-loop Joule-Thomson coolers. In response to a need for very high resolution midwave IR (MWIR) detectors and systems, SCD has developed a large format 2D InSb detector with 1280×1024 elements and pixel size of 15 μm. The ROIC is fabricated in CMOS 0.18-μm technology, that enables the small pixel circuitry and relatively low power generation at the focal plane. The digital ROIC has an analog to digital (A/D) converter per-channel and allows for full frame readout at a rate of 100 Hz. Such on-chip A/D conversion eliminates the need for several A/D converters with fairly high power consumption at the system level. The digital readout, together with the InSb detector technology, lead to a wide linear dynamic range and low residual nonuniformity, which is stable over a long period of time following a nonuniformity correction procedure. A special Dewar was designed to withstand harsh environmental conditions while minimizing the contribution to the heat load of the detector. The Dewar together with the low power ROIC, enable a megapixel detector with overall low size, weight, and power with respect to comparable large format detectors. A variety of applications with this detector make use of different cold shields with different f-number and spectral filters. In this paper we present actual performance characteristics of the megapixel InSb detector and demonstrate its high manufacturability.

High-performance IR detectors at SCD present and future

AbstractFor over 27 years, SCD has been manufacturing and developing a wide range of high performance infrared detectors, designed to operate in either the mid-wave (MWIR) or the long-wave (LWIR) atmospheric windows. These detectors have been integrated successfully into many different types of system including missile seekers, time delay integration scanning systems, hand-held cameras, missile warning systems and many others. SCD’s technology for the MWIR wavelength range is based on its well established 2D arrays of InSb photodiodes. The arrays are flip-chip bonded to SCD’s analogue or digital signal processors, all of which have been designed in-house. The 2D focal plane array (FPA) detectors have a format of 320×256 elements for a 30-μm pitch and 480×384 or 640×512 elements for a 20-μm pitch. Typical operating temperatures are around 77–85 K. Five years ago SCD began to develop a new generation of MWIR detectors based on the epitaxial growth of antimonide based compound semiconductors (ABCS). This ABCS technology allows band-gap engineering of the detection material which enables higher operating temperatures and multi-spectral detection. This year SCD presented its first prototype FPA from this program, an InAlSb based detector operating at a temperature of 100 K. By the end of this year SCD will introduce the first prototype MWIR detector with a 640×512 element format and a pitch of 15 μm. For the LWIR wavelength range SCD manufactures both linear Hg1−xCdxTe (MCT) detectors with a line of 250 elements and time delay and integration (TDI) detectors with formats of 288×4 and 480×6. Recently, SCD has demonstrated its first prototype uncooled detector which is based on VOx technology and which has a format of 384×288 elements, a pitch of 25 μm, and a typical NETD of 50 mK at F/1. In this paper, we describe the present technologies and products of SCD and the future evolution of our detectors for the MWIR and LWIR detection.

Advanced Column-IV Epitaxial Materials for Silicon-Based Optoelectronics

Over the past decade or so, research in silicon-based heterostructures has evolved from a few seminal publications on the growth and physical properties of Si1−xGex heteroepitaxial layers to a technology currently entering large-scale commercial production for heterojunction bipolar transistors (HBTs). During this period, extensive work has taken place on the optoelectronic applications of Si/Si1−x Gex such as 1.3–1.55 μam detectors for optical communication, 2–12-μm infrared detectors for two-dimensional (2D) focal plane arrays for night vision and thermal imaging, and infrared emitters for chip-to-chip optical communication as well as waveguiding and modulators. The overall goal of this work has been to merge optoelectronic functionality with the very large-scale-integration and electronic signal processing capabilities of silicon to create a silicon-based “superchip.”