新型离子注入形成吸收层的平面型GaAs基阻挡杂质带探测器及其制备研究

Recently, Due to the advantages of making large-format array and extending detection wavelength, etc., GaAs-based blocked-impurity-band (BIB) detectors exhibit excellent application prospects in the area of space-based terahertz (THz) detection. However, due to the restrictions from material quality and device processing, the traditional liquid-phase-epitaxy (LPE) grown mesa GaAs-based BIB detectors have disadvantages including poor reproducibility, large dark current, and low responsivity. A novel planar GaAs-based BIB detector with the absorption layer formed by ion implantation is proposed. This project is planned to adopt the design of growing the blocking layer on the high-resistivity GaAs substrate in order to increase the purity of the blocking layer, and thus reduce the dark current. The design of forming the absorption layer with ion implantation will be adopted in this project, making the doping concentration of the absorption layer highly controllable, and thus the device reproducibility improved. Additionally, the planar design will be adopted as well, for suppressing the surface defects, and thus reducing dark current and enhancing responsivity. The complete device model is constructed by combining theory and experiment together, in order to achieve three objectives: (1) improving device fabrication technology; (2) revealing the effects of key device parameters and ion implantation conditions on THz absorption and impurity-band transition; (3) elucidating the mechanisms of dark current and noise under different biases and temperatures. Our final goal is to develop the original GaAs-based BIB devices with high performances.

近年来，GaAs基阻挡杂质带（BIB）探测器由于具有制作大面阵和延伸探测波长等优势，在天基太赫兹（THz）探测领域展现出极好的应用前景。但由于受当前材料质量和器件工艺的限制，传统液相外延生长的台面型GaAs基BIB探测器存在可重复性差、暗电流大、响应率低的缺点。本项目提出一种新型离子注入形成吸收层的平面型GaAs基BIB探测器，拟采用在高阻GaAs衬底上生长阻挡层的设计提高阻挡层纯度，从而降低暗电流；采用离子注入形成吸收层的设计，可以使吸收层掺杂浓度高度可控，从而提高器件可重复性；采用平面型设计，可以抑制表面缺陷，从而降低暗电流以及提高响应率。通过理论与实验相结合，建立完备的器件模型，在完善制备工艺的同时，揭示器件关键设计参数和离子注入条件对THz吸收和杂质带跃迁的影响规律及其机理；阐明不同偏压和温度下器件暗电流和噪声的物理机制，并最终研制出高性能GaAs基BIB原型器件。

项目背景.太赫兹辐射是介于微波与红外之间的电磁波。GaAs基阻挡杂质带（BIB）探测器作为一种新型太赫兹探测器，可基于光电子技术实现对太赫兹辐射的探测。其探测原理有别于传统电子学太赫兹探测器（从微波向高频方向突破），它是从红外向低频方向突破，来实现太赫兹探测。BIB探测器与传统太赫兹探测器相比，具有灵敏度高、阵列规模大、响应谱段宽等优势，在大气监测、天文观测、人体隐匿物检测、炸药及毒品监测领域具有广阔的应用前景。.主要研究内容.（1）器件制备工艺与测试方法研究；.（2）掺杂元素及浓度对器件性能的影响；.（3）拟研制器件的杂质带跃迁和暗电流、噪声机理研究。.重要结果、关键数据及其科学意义.（1）经过光刻标记制作、吸收层制作、电极层制作、钝化层制作、欧姆电极制作、加厚电极制作等六步工艺完成了GaAs基BIB探测芯片的制备。进而，采用黑体响应测试系统和傅里叶光谱响应测试系统分别测试了GaAs基BIB探测器的黑体响应及光谱响应特性，结果表明器件的黑体响应率为37.3 mA/W，响应频率覆盖1.5~5 THz，响应峰值波长大于200 μm；.（2）研究了Si、B等受主杂质元素及浓度对GaAs基BIB探测器性能的影响，结果表明响应率和暗电流均是Si、B等受主杂质浓度的单调递减函数，从而证实了受主杂质浓度是探测器性能的敏感参数，且为探测器性能优化提供了可靠依据；.（3）针对GaAs基BIB探测器国际上最为关心的物理问题，阐明了器件关键功能层（阻挡层与吸收层）在杂质带跃迁及其传输机理中所起的作用，证明了暗电流及光响应的大小仅取决于吸收层内的电场强度，而与阻挡层内的电场强度无关，但由于阻挡层对吸收层的电场调制效应，暗电流及光响应的大小实际上取决阻挡层的厚度；.（4）证明了GaAs基BIB探测器存在两种载流子输运模式，即电子电流模式及跳跃电流模式，且对探测器性能起决定性作用的是电子电流模式；.（5）明确了GaAs基BIB探测器的暗电流及噪声机制由漂移扩散电流和产生复合电流共同主导。