Development of Tera-hertz Large-format Imaging Devices

目前，Ge: Ga光导体是制造大型阵列探测器中最灵敏的太赫兹探测器。然而，为了降低暗电流和提高噪声性能，掺杂剂密度的降低会导致光子吸收系数的降低，因此很难减小探测器的物理尺寸。因此，数组格式的显著增加应该是非常困难的。为了避免这一障碍，提出了阻塞杂质带结构（Madarsz和Szmulowicz， 1987）。多层探测器由用于有效光子吸收的高掺杂层和用于阻断暗电流的高纯度层组成，使探测器具有低暗电流的高灵敏度。然而，为了制造这种探测器结构，成熟的晶体生长技术是不可避免的。因此，天文质量的锗探测器尚未实现，为了在现有技术下实现这种探测器结构，我们计划应用晶圆键合技术。该技术是通过热处理和机械应力将两个独立的晶片粘合在一起，制成具有清晰晶体组成边界的单晶。研究结果表明，我们成功地制备了具有bib型电性能的探测器材料，并展示了用于锗表面抗反射的大幅面硅透镜阵列的前景。因此，我们可以得出结论，成功地证明了开发大尺寸高灵敏度太赫兹探测器阵列的巨大可能性。

Currently, Ge : Ga photoconductors are the most sensitive THz detectors for fabrications of large-format array detectors. To reduce dark current and improve noise performance, however, the reduction of dopant density leads to degradation of photon absorption coefficients and thus it is difficult to reduce the physical size of the detector. As the results, the significant increase of array format should be highly difficult.To avoid this obstacle, Blocked Impurity Band structure is proposed (Madarsz and Szmulowicz, 1987). Multi-layer detector consists of high-doped layer for efficient photon absorption and high-purity layer for blocking dark current makes high sensitive detector with low dark current.To fabricate this detector structure, however, mature technology for crystal growth is inevitable. Ge detector of astronomical quality is thus not yet realizedTo realize this detector structure with available technology, we plan to apply wafer-bonding technique. This technique is to bond two independent crystal wafers with thermal annealing and mechanical stress to make single crystal with sharp boundary of the crystal composition.As the result of our investigation, we succeeded to fabricate detector material with BIB-type electric properties as well as to demonstrate the prospects for large-format Si lens array for anti-reflection on Ge surface. We can thus conclude that great possibilities for developing large-format high-sensitive THz detector array is successfully demonstrated.