Investigation On Novel Terahertz Detection Physics And Device

Terahertz(THz) wave detection is one of the critical and foundamental research fields in the area of terahertz physics and its applications. Development of terahertz detection technology in imaging, remote sensing, security, biomedicine and communication requires much effort in developing high performance terahertz detector. Terahertz detection technology with high sensitivivity, fast response speed, easy to fabricate to large array and room temperature operation is currently one of the urgent directions that required to be fully developed in terahertz related fields. Focusing on terahertz detection physics, this thesis proposes an obvious photoconductivity at room temperature and further deduces a physical model for high performance terahertz detection. By exploring technical processes of narrow gap semiconductor, real terahertz detectors based on Hg Cd Te and In Ga As materials were fabricated. And their performance was characterized by some home-made measurement setups. We also made a preliminary study about the designing of infrared and sub-terahertz passive scanning imager. Multiband imaging was realized by mounting detectors covering ranges from infrared to sub-terahertz wave. This thesis also makes a preliminary-stage investigation about infrared photodetection based on N-Ga Sb/n-In As Sb heterojunction. The main contexts and novel points are as follows:1. Based on the classical theory of electromagnetic wave, combined with the metal-semiconductor-metal subwavelength structure, we proposed a novel photoconductivity method at room temperature. It makes a breakthrough for generating photoconductivity that traditionally based on interband, intraband, and impurity transitions. This novel physical mechanism has huge potential in high performance low quantum energy photodetection.2. Based on narrow gap semiconductor Hg Cd Te material, we experimentally fabricated various metal-semiconductor-metal structures with different size to demonstrate the strong photoconductivity at room temperature.3. Based on the proposed novel theory on strong photoconductivity at room temperature, a new physical model regarding to terahertz detection was derived. And we did some quantitative and qualitative simulation about the detection model by COMSOL and HFSS softwares. Furthermore, by exploring the technical process of narrow gap semiconductor Hg Cd Te and In Ga As, real terahertz detectors based on these two materials were fabricated.4. We fabricated measuremental setups to characterize the terahertz detector. And we used an IMPATT to measure the performance of the devices. We used the FTIR to measure the spectral response of the MCT detector at terahertz range. The Noise Equivalent Power(NEP), detectivity and some other figure of merits of the Hg Cd Te terahertz detector were obtained. And the performance of the Hg Cd Te terahertz detector is 2-3 orders higher than other types of room temperature terahertz detectors. The measured respond time of the Hg Cd Te detector was at least better than 1 μs.5. We made a preliminary stage exploring on infrared and sub-terahertz imaging. By utilizing a passive scanning imager, combined with different type of detectors(a commercial Ga As P-N junction 94 GHz detector, a commercial thermopile, a homemade Mn1.56Co0.96Ni0.48O4(MCN) bolometer, and a homemade VO2 bolometer), infrared to sub-terahertz multiband passive scanning imaging was realized.6. We did some preliminary researchs about infrared photodetection based on N-Ga Sb/n-In As Sb heterojunction. Spectral responses obtained at different bias voltage and different temperature showed this type of heterojunction detector had the ability of dual color detection covering wavelength range from near infrared to middle infrared wave at room temperature.