This Chapter covers recent advances in Short Wavelength Infrared (SWIR), Medium Wave‐ length Infrared (MWIR) and Long Wavelength Infrared (LWIR) materials and device technol‐ ogies for a variety of defense and commercial applications. Infrared technology is critical for military and security applications, as well as increasingly being used in many commercial products such as medical diagnostics, drivers’ enhanced vision, machine vision and a multi‐ tude of other applications, including consumer products. The key enablers of such infrared products are the detector materials and designs used to fabricate focal plane arrays (FPAs).

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Advances in Infrared Detector Array Technology

A photoluminescence study of polycrystalline thin-film CdTe/CdS solar cells

Heteroepitaxy of CdTe on {211}Si substrates by molecular beam epitaxy

Spatially resolved characterization of HgCdTe materials and p-n junction diodes using scanning laser microscopy is reviewed. Several techniques that yield spatial maps of electrical inhomogeneities in HgCdTe material and non-uniformities in various performance parameters of p-n junctions fabricated using these materials have been developed. Many of the techniques are non-destructive, or can be made such with minor changes in sample preparation, and are scalable to large full wafers. A high-resolution and non-destructive technique called 'laser beam induced current (LBIC)' has been developed for spatial mapping of electrically active regions in HgCdTe. When applied to unprocessed HgCdTe material, LBIC images represent spatial distributions of electrically active defects including inclusions, strain, damage, precipitates, stacking faults, twin boundaries, dislocation clusters, bandgap and doping variations. Device structures such as p-n junctions are special cases of electrically active regions, therefore the LBIC technique lends itself to a non-destructive study of p-n junction arrays without requiring any direct electrical contact to the individual elements of the array. The remote contacting, especially using pressure contacts, makes the application of the LBIC technique non-destructive, allowing testing at various stages of device processing to identify particular processing procedures that need optimization. LBIC has also been used to spatially map electrical non-uniformities at the HgCdTe surface near its interface with an insulating passivation layer. Besides LBIC imaging, scanning laser microscopy has been used for several other applications. For HgCdTe p-n junctions, applications include photoresponse mapping (uniformity, active area and diffusion length determination, contact bonding effects), spatially resolved light-induced degradation, and avalanche photodiode properties (ionization coefficients, localized breakdown). A key technique currently in development is the non-contact diode R0A determination based on trapping mode photoconductivity. Examples of scanning laser microscopy on HgCdTe materials are infrared transmission mapping (thickness and bandgap variations), photoluminescence mapping, and minority carrier lifetime mapping (distribution of recombination centres).

http://iopscience.iop.org/article/10.1088/0268-1242/8/6S/008/pdf

Spatially resolved characterization of HgCdTe materials and devices by scanning laser microscopy

Close lattice matching and lattice compatibility with mercury cadmium telluride (MCT) make CdTe and related alloys ideal substrate materials for growth of MCT layers for the purpose of making high-performance second-generation infrared detectors. However, the limitations in the properties of CdTe and the difficulties in its bulk growth have prompted extensive research in the area of alternative substrates. Some basic relevant characteristics of substrates such as sapphire, GaAs, and silicon are compared and the possibilities and problems associated with each material are analyzed in the light of the most recent results in the field.

W.E. Tennant

Papers

HgCdTe on sapphire — A new approach to infrared detector arrays

Remote contact LBIC imaging of defects in semiconductors

Spatial origin of various PL lines in CdTe at 77 K