A thermal sensitive infrared and THz detector was fabricated by a double layered Mn-Co-Ni-O/Mn-Co-Ni-Cu-O films. The Mn-Co-Ni-O material, as one type of transition metal oxides, has long been used as a candidate for thermal sensors or infrared detectors. The resistivity of a most important Mn-Co-Ni-O thin film, Mn<sub>1</sub>. <sub>96</sub>Co<sub>0.96</sub>Ni<sub>0.48</sub>O<sub>4</sub>(MCN) , is about 200 Ω·cm at room temperature, which ranges about 2 orders larger than that of VOx detectors. Therefore, the thickness of a typical squared Mn-Co-Ni-O IR detector should be about 10 μm, which is too large for focal plane arrays applications. To reduce the resistivity of Mn-Co-Ni-O thin film, 1/6 of Co element was replaced by Cu. Meanwhile, a cover layer of MCN film was deposited onto the Mn-Co-Ni-Cu-O film to improve the long term stability. The detector fabricated by the double layered Mn-Co-Ni-O/Mn-Co-Ni-Cu-O films showed large response to blackbody and 170 GHz radiation. The NEP of the detector was estimated to be the order of 10<sup>-8</sup> W/Hz<sup>0. 5</sup>. By applying thermal isolation structure and additional absorption materials, the detection performance can be largely improved by 1-2 orders according to numerical estimation. The double layered Mn-Co-Ni-O film detector shows great potentials in applications in large scale IR detection arrays, and broad-band imaging.
High sensitive Terahertz detection can be achieved by properly constructing Metal-Semiconductor-Metal (MSM) structure with semiconductor materials. In this study, Mercury-Cadmium-Telluride (MCT) film was used to fabricate MSM Terahertz detectors. The working temperature was altered to study the IV characteristics of MCT detectors under RT and 77 K, as well as the response signals to 0.0375 THz and 150 GHz sources. The results showed that the response speed was greatly improved under low temperature condition, and the time constant decreased to smaller than 3 μs at 77 K, comparing to some hundred μs at room temperature (RT). However, due to the variation in IV characteristics under low temperature, the working current of the detector was much lower than that at RT for identical voltage bias, and the low frequency response was 6 times larger than that at RT under the same bias current. The MCT detector is shown to be highly sensitive for THz detection and its detection ability can be further improved by lowering down the working temperature.
A terahertz photodetector was designed based on the novel room-temperature photoconductivity theory we proposed before. Prototype detectors with different sizes of photo-active area was fabricated on In<sub>0.53</sub>Ga<sub>0.47</sub>As material. Detectors' I-V property were tested, and signal response to a 0.0375THz source were measured. Results indicated that our detectors performed outstanding responsivity and respond speed. The room-temperature responsivity was estimated to be on the order of 10<sup>4</sup> V/W, the corresponding noise equivalent power (NEP) was estimated to be on the order of 10<sup>-12</sup> W/Hz<sup>1/2</sup>, and the response time constant was calculated to be 1.06×10<sup>-5</sup> S. Finally, our room-temperature photoconductivity theory was confirmed to be detectors’ respond mechanism via experiment and estimation.