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.
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.
In order to fabricate low cost and printable CuInSe<sub>2</sub> (CIS) thin film solar cells, a chemical process has been developed to fabricate uniform CIS films with large grain size and close stoichiometry to chalcopyrite phase. Cu(NO<sub>3</sub>)<sub>2</sub>, InCl<sub>3</sub> and ethyl cellulose (EC) were adopted to form the starting solution. CIS films were prepared by spin-coating and selenization. Precursor films and CIS films were investigated by SEM, EDS and XRD. CuCl and InCl<sub>3</sub> crystals appeared in the precursor films. During the selenization process, CuCl first reacted with Se vapor to form Cu<sub>2-x</sub>Se. With increasing selenization temperature, InCl<sub>3</sub> reacted with Cu<sub>2-x</sub>Se to form CIS accompanying the evaporation of chlorine in the form of gas. It is revealed that the element ratio in final CIS film is determined by the raw material ratio in the starting solution and the selenization temperature.
Al doped ZnO (ZnO:Al, AZO) thin films were deposited on ordinary soda-lime glass (SLG) substrates by RF magnetron sputtering. Effects of post annealing (300~600 °C for 2~30 min in air and N<sub>2</sub>, respectively) were studied. All the films were wurtzite structure with highly c-axis preferential orientation. Their electrical properties were relatively stable at the post annealing temperature of 300 °C. As the temperature further increasing, post annealing in air leaded to drastic degradation in the electrical properties, while that in N<sub>2</sub> had relatively small influence. Diffusion of alkali ions from SLG substrates was deduced to be one of the influence factors for electrical properties. The spectra measurements showed that the post annealing mainly affected the transmittance in the near-infrared and infrared (NIR-IR) range and the optical band gap (E<sub>g</sub>). The variation of E<sub>g</sub> was attributed to the Burstein-Moss (BM) shift modulated by many-body effects.