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Detectors composed of novel Antimonide Based Compound Semiconductor (ABCS) materials offer some unique advantages. InAs/GaSb type II superlattices (T2SL) offer low dark currents and allow full bandgap tunability from the MWIR to the VLWIR. InAs1-xSbx alloys (x~0.1) also offer low dark currents and can be used to make MWIR devices with a cut-off wavelength close to 4.2μm. Both can be grown on commercially available GaSb substrates and both can be combined with lattice matched GaAlSbAs barrier layers to make a new type of High Operating Temperature (HOT) detector, known as an XBn detector. In an XBn detector the Generation-Recombination (G-R) contribution to the dark current can be suppressed, giving a lower net dark current, or allowing the same dark current to be reached at a higher temperature than in a conventional photodiode. The ABCS program at SCD began several years ago with the development of an epi-InSb detector whose dark current is about 15 times lower than in standard implanted devices. This detector is now entering production. More recently we have begun developing infrared detectors based both on T2SL and InAsSb alloy materials. Our conventional photodiodes made from T2SL materials with a cut-off wavelength in the region of 4.6μm exhibit dark currents consistent with a BLIP temperature of ~ 120-130K at f/3. Characterization results of the T2SL materials and diodes are presented. We have also initiated a program to validate the XBn concept and to develop high operating temperature InAsSb XBn detectors. The crystallographic, electrical and optical properties of the XBn materials and devices are discussed. We demonstrate a BLIP temperature of ~ 150K at f/3.

The preparation of high quality polypyrrole film in aqueous solutions is described. The new polypyrrole films were produced in a phthalate buffer solution (pH 4) with perchlorate as the electrolyte. Very smooth and remarkably flexible free-standing films were grown electrochemically. The conductivity of the polypyrrole film exhibits an inverse dependency on the film thickness. The mechanical properties of these films, such as tensile strength and the modulus of elasticity, are better than the reported properties for polypyrrole/tosylate films prepared in organic solutions. In comparison with the polypyrrole films prepared in phosphate buffer solution, the stability of the polypyrrole films prepared in phthalate buffer are improved considerably. The morphology and composition of the conducting film is described and a mechanism for their formation is proposed.

Antimonide Based Compound Semiconductors (ABCS) and a new family of advanced analogue and digital silicon read-out integrated circuits form the basis of the SCD 3rd generation detector program, which builds on the firm platform of SCDs existing InSb-FPA technology. We have devised a staged roadmap at SCD which begins with epitaxial InSb mesa diodes and gradually increases in technological sophistication. In the initial stages we have focused in particular on In 1-z Al z Sb alloys grown on InSb by Molecular Beam Epitaxy (MBE). Some of our achievements with these materials are presented in this paper. For epitaxial InSb (z = 0), we demonstrate the performance of Focal Plane Arrays (FPAs) with a format of 320x256 pixels, at focal plane temperatures between 77K and 110K. An operability has been achieved which is in excess of 99.5%, with a Residual Non-Uniformity (RNU) at 95K of less than 0.03% (standard deviation/dynamic range) between 15 and 80% well fill. Moreover, after a two point Non-Uniformity Correction (NUC) has been applied at 95K, the RNU remains below ~0.1% at all focal plane temperatures down to 85K and up to 100K without the need to apply any further correction. This is a major improvement in both the temperature of operation and the temperature stability compared with implanted diodes made from bulk material. We also demonstrate rapid progress in the development of epitaxial InAlSb FPAs with comparable operability and RNU to the InSb FPAs but which exhibit lower dark current and offer a range of cut-off wavelengths shorter than in InSb. These FPAs are intended for temperatures of operation in excess of 100K.

Antimonide Based Compound Semiconductors (ABCS) and a new family of advanced analogue and digital silicon read-out integrated circuits form the basis of the SCD 3rd generation detector program, which builds on the firm platform of SCDs existing InSb-FPA technology. In order to cover the MWIR atmospheric window, we recently proposed the epitaxial alloys: InAs1-y Sby on GaSb with 0.07 < y < 0.11 and In1-zAlz Sb on InSb with 0 < z < 0.03. In this paper we focus on the results of some of our recent work on epitaxial In1-zAlz Sb grown on InSb by Molecular Beam Epitxay (MBE). In epitaxial InSb (z = 0), we demonstrate the performance of Focal Plane Arrays (FPAs) with a format of 320x256 pixels, at focal plane temperatures between 77K and 100K. An operability has been achieved which is in excess of 99.5%, with a Residual Non-Uniformity (RNU) at 95K of less than 0.03% (standard deviation/dynamic range). Moreover, after a two point Non-Uniformity Correction (NUC) has been applied at 95K, the RNU remains below ~0.1% at all focal plane temperatures down to 85K and up to 100K without the need to apply any further correction. This is a major improvement in both the temperature of operation and the temperature stability compared with implanted diodes made from bulk material. We also demonstrate rapid progress in the development of low current epitaxial InAlSb photodiodes with high uniformity and low dark current that offer a range of cut-off wavelengths shorter than in InSb. Preliminary results are presented on FPAs with a cut-off wavelength in the range λC~5μ.