基于频率上转换的异质结太赫兹成像的物理及器件研究

太赫兹(THz)成像在空间探索、环境监测、及安全反恐等领域具有重大应用前景。本课题提出一种基于频率上转换的异质结太赫兹无像元成像方案。将异质结界面功函数内光发射探测器（HEWIP）与发光二极管（LED）集成形成频率上转换器件。入射的太赫兹信号在一个大面积的HEWIP-LED器件单元中上转换为近红外信号，被性能成熟的CCD探测，实现太赫兹无像元成像。通过深入理解器件在低温弱信号下的光吸收、载流子输运和复合特性及光-电-光转换中的噪声机制等一系列物理问题，设计和优化上转换器件结构和参数，摸索制备工艺，解决电势分配、局部热点及出光效率等核心问题，获得大面积单元的器件，并在此基础上实现无像元成像。这种成像器件无需使用读出电路，避免了采用光子型太赫兹焦平面阵列成像中读出电路的低温互联问题，具有探测率高、响应速度快、宽波段响应的优点，迎合了高性能太赫兹成像的需求，是当前太赫兹成像的重要选择。

Terahertz imaging has many potential applications, such as space exploration, environment monitoring, as well as safety and anti-terrorism etc.. In this project, we propose a terahertz imager based on the frequency up-conversion technique by integrating a heterojunction interfacial work function internal photoemission (HEWIP) detector and a near-infrared light emitting diodes (LEDs). The incident terahertz signal is up-converted to the near infrared radiation through the large-sized cell of HEWIP-LED upconverter, and then detected by a Si charge coupled device (CCD). Thereby, the terahertz pixelless imaging is realized. Through the deep understanding of a series of physical problems, including the weak light absorption, the carrier transport and recombination, as well as the noise mechanism in the photon-current-photon conversion process under low temperature, the upconverter is designed and optimized deliberately. Some investigations, such as the reasonable distribution of electric potential, the local hot spots and the light efficiency would be performed. The key fabrication processes are developed to acquire the large unit device, thus the pixelless imaging is be realized. Due to the great advantage of avoiding the silicon readout circuits, it can overcome the possible failure resulted from thermal mismatch, which is a big technical challenge encountered in the traditional photon-type terahertz focal plane arrays. The proposed device has the advantage of high detection sensitivity, fast response speed, and wide wavelength coverage, which meets the demand of the high-performanced THz imaging, making it an important choice for terahertz imaging.