Borys P. Kolasa

Electrochromic devices and thin film transistors from a new family of ethylenedioxythiophene based conjugated polymers

New electrochromic conjugated polymers and their corresponding devices based on EDOT (ethylenedioxythiophene) are described. The best of these polymers display response times on the order of 1s and high switchable contrast in the visible and near-infrared (Vis-NIR) spectral regions. Thin films (70 nm) of these new polymers displayed optical band gaps on the order of 1.73 eV (7a) < 2.19 eV (7b) < 2.23 eV (7c) < 2.31 eV (4) < 2.34 eV (2) as calculated from their extrapolation of the absorption edges. Polymers 4 and 7a show field effect hole mobilities of ca. 6.7 × 10−5 cm2 V−1s−1 (on/off ratio 104) and 2.5 × 10−5 cm2 V−1s−1 (on/off ratio103), respectively, related to their highly ordered inter-chain packing as confirmed by XRD analyses of polymer 4. Electrochromic characterizations show that polymers 7a–c exhibit significant absorption changes in the infrared at low voltage. The resulting solid-state devices offer promise for electrochromic shutters and filters in the IR, since their high charge transfer mobility and ion injection efficiency permits relatively rapid switching and good switchable contrast, while their robustness exceeds that of aqueous devices.

Characterization of barrier effects in superlattice LWIR detectors

Improved LWIR sensors are needed for defense applications. We report an advance in sensor technology based on diodes in type-II strained layer superlattice structures built in the InAs/GaSb/AlSb materials system. A key feature of the devices is a pair of complementary barriers, namely, an electron barrier and a hole barrier formed at different depths in the growth sequence. The structure is known as CBIRD. This work is a collaborative effort between Raytheon Vision Systems and Jet Propulsion Laboratory, with design and growth being performed at JPL, and processing and testing at RVS. We have analyzed the current-voltage characteristics as functions of temperature and junction area, and have measured the spectral response and quantum efficiency as functions of bias voltage. From the temperature dependence of the dark current in a typical case, we infer that the effective barrier height is 0.175 eV. This indicates that dark current is limited by the barriers rather than diffusion or GR mechanisms occurring within the absorber region where the bandgap is 0.13 eV. The barriers prove to be very effective in suppressing the dark current. In the case of a detector having a cutoff wavelength of 9.24 μm, we find R0A > 105 ohm cm2 at 78 K, as compared with about 100 ohm cm2 for an InAs/GaSb homojunction of the same cutoff. For good photo response, the device must be biased to typically -200 or -250 mV. In this condition we find the internal quantum efficiency to be greater than 50%, while the RA remains above 104 ohm cm2. Thus, the device shows both high RA and good quantum efficiency at the same operating bias. We have also measured the capacitance of the CBIRD device as functions of bias and frequency to help characterize the behavior of the barriers. A 256×256 focal plane array was fabricated with this structure which showed at 78K a responsivity operability of more than 99%.

Scaled carbon-ionogel supercapacitors for electronic circuits

Capacitors are ubiquitous in signal processing circuits. Dielectric capacitors based on metal-oxide-semiconductor (MOS) and metal-insulator-metal (MIM) designs are currently the industry standard for on-chip charge storage. By comparison, electric double-layer capacitors (EDLC), or supercapacitors, offer capacitances that are orders of magnitude higher than dielectric capacitors. In this paper we present some early work in fabricating solid-state, on-chip EDLC.

Antenna Coupled Detectors for 2D Staring Focal Plane Arrays

Millimeter-wave (mmW)/sub-mmW/THz region of the electro-magnetic spectrum enables imaging thru clothing and other obscurants such as fog, clouds, smoke, sand, and dust. Therefore considerable interest exists in developing low cost millimeter-wave imaging (MMWI) systems. Previous MMWI systems have evolved from crude mechanically scanned, single element receiver systems into very complex multiple receiver camera systems. Initial systems required many expensive mmW integrated-circuit low-noise amplifiers. In order to reduce the cost and complexity of the existing systems, attempts have been made to develop new mmW imaging sensors employing direct detection arrays. In this paper, we report on Raytheon’s recent development of a unique focal plane array technology, which operates broadly from the mmW through the sub-mmW/THz region. Raytheon’s innovative nano-antenna based detector enables low cost production of 2D staring mmW focal plane arrays (mmW FPA), which not only have equivalent sensitivity and performance to existing MMWI systems, but require no mechanical scanning.