Challenges of small-pixel infrared detectors: a review

Abstract

In the last two decades, several new concepts for improving the performance of infrared detectors have been proposed. These new concepts particularly address the drive towards the so-called high operating temperature focal plane arrays (FPAs), aiming to increase detector operating temperatures, and as a consequence reduce the cost of infrared systems. In imaging systems with the above megapixel formats, pixel dimension plays a crucial role in determining critical system attributes such as system size, weight and power consumption (SWaP). The advent of smaller pixels has also resulted in the superior spatial and temperature resolution of these systems. Optimum pixel dimensions are limited by diffraction effects from the aperture, and are in turn wavelength-dependent. In this paper, the key challenges in realizing optimum pixel dimensions in FPA design including dark current, pixel hybridization, pixel delineation, and unit cell readout capacity are outlined to achieve a sufficiently adequate modulation transfer function for the ultra-small pitches involved. Both photon and thermal detectors have been considered. Concerning infrared photon detectors, the trade-offs between two types of competing technology-HgCdTe material systems and III-V materials (mainly barrier detectors)-have been investigated.

Transparent Heaters: A Review

“…The pixel pitch of these cameras has decreased to 10 μm, and recent studies suggest that it can be lowered down to 5 μm. [ 100 ] Other critical issues of IR imaging are emissivity and reflection. In modern IR cameras these parameters can generally be set by the operator.…”

Nanostructured Materials and Architectures for Advanced Infrared Photodetection

“…As a result, photovoltaic detectors are capable to work with almost zero dark current. This characteristic is particularly useful in infrared photodetectors when integrated in FPAs, since it avoids the charge saturation in readout circuits by the notorious dark current in narrow bandgap materials . Figure b illustrates the charge separation under the photovoltaic effects.…”

“…From the perspective of light coupling to the tiny photodetectors beyond the diffraction limit, remarkable progresses have been also made in enhancing the light‐matter interaction in the subwavelength volume, by using plasmonic nanostructures and metamaterials . Upon integration in focal plane arrays (FPA), this improvement provides a solution toward high resolution infrared imaging sensors for thermal imaging . These achievements from different aspects of a photodetector (detectivity, speed, operation temperature, etc.)…”

Design and Development of Two-Dimensional Strained Layer Superlattice (SLS) Detector Arrays for IR Applications

“…Due to the absence of majority carrier flow, the nBn detector (Figure 13) [84,85] is essentially a photoconductor with unity gain, in which the junction (space charge region) is replaced by an electron blocking unipolar barrier (B) and the p-contact by an n-contact [8]. The wide bandgap undoped barrier layer is chosen to have minimal valence band offset [86].…”