Development of Tera-hertz Large-format Imaging Devices

目前，Ge：Ga光电导体是制作大尺寸阵列探测器的最灵敏的THz探测器。然而，为了减少暗电流并改善噪声性能，掺杂剂密度的降低导致光子吸收系数的劣化，因此难以减小检测器的物理尺寸。因此，阵列格式的显著增加应该是非常困难的，为了避免这个障碍，提出了阻塞杂质带结构（Madarsz和Szmulowicz，1987）。多层探测器是由高掺杂层和高纯度层组成，高掺杂层用于有效吸收光子，高纯度层用于阻挡暗电流，使得探测器具有高灵敏度和低暗电流，但要制备这种探测器结构，必须有成熟的晶体生长技术。因此，天文质量的Ge探测器尚未实现。为了利用现有技术实现这种探测器结构，我们计划应用晶片键合技术。该技术是通过热退火和机械应力将两片独立的单晶片键合在一起，使单晶具有清晰的晶体成分边界，成功地制备出了具有BIB-type电性能的探测器材料，并展示了大尺寸Si透镜阵列在Ge表面减反射的前景。因此，我们可以得出结论，大幅面高灵敏度的太赫兹探测器阵列的开发成功展示了巨大的可能性。

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.