针对太赫兹通信及成像等系统对高集成度射频收发链路的需求, 在自主研制的太赫兹肖特基二极管的基础上, 建立了器件的精确模型, 设计并制备出基于二极管的倍频/混频单片集成芯片, 解决了传统二极管装配难度大、一致性差的难题, 提高了器件的性能。成功研制出170 GHz、340 GHz倍频器和340 GHz混频器模块, 并且开发出集成化的340 GHz发射与接收链路。发射端一体化模块实现了342 GHz功率为22 mW的输出, 接收端一体化模块实现了330～350 GHz单边带变频损耗在10 dB上下。该模块的开发为未来太赫兹通信及成像技术的应用奠定基础。

In this work, high-stability 4H-SiC avalanche photodiodes (APDs) for ultraviolet (UV) detection at high temperatures are fabricated and investigated. With the temperature increasing from room temperature to 150°C, a very small temperature coefficient of 7.4 mV/°C is achieved for the avalanche breakdown voltage of devices. For the first time, the stability of 4H-SiC APDs is verified based on an accelerated aging test with harsh stress conditions. Three different stress conditions are selected with the temperatures and reverse currents of 175°C/100 µA, 200°C/100 µA, and 200°C/500 µA, respectively. The results show that our 4H-SiC APD exhibits robust high-temperature performance and can even endure more than 120 hours at the harsh aging condition of 200°C/500 µA, which indicates that 4H-SiC APDs are very stable and reliable for applications at high temperatures.

基于最新研制的小阳极结反向并联肖特基二极管芯片，设计和制造了320~360 GHz固定调谐分谐波混频器。混频器的结构采用的是传统电场（E）面腔体剖分式结构：将二极管芯片倒装焊粘在石英基片上，再用导电银胶将石英电路悬置粘结在混频器下半个腔体上。电路设计采用场路相结合的方法：用场仿真软件建立混频电路各个功能单元的S参数模型，将它们代入非线性电路仿真软件中与二极管结相结合进行混频器性能整体仿真优化。最终测试结果表明，谐波混频器的双边带在4~6 mW的本振功率驱动下，在320~360 GHz超过12%带宽范围内，双边带变频损耗均小于9 dB；混频器在310~340 GHz频带范围内，双边带噪声温度最低为780 K。声温度最低为780 K。

Metasurfaces have powerful light field manipulation capabilities and have been researched and developed extensively in various fields. With an increasing demand for diverse functionalities, terahertz (THz) metasurfaces are also expanding their domain. In particular, integrating different functionalities into a single device is a compelling domain in metasurfaces. In this work, we demonstrate a functionally decoupled THz metasurface that can incorporate any two functions into one metasurface and switch dynamically through external excitation. This proposed metasurface is formed by the combination of split-ring resonators and phase change material vanadium dioxide (VO2). It operates in the single-ring resonant mode and double-ring resonant mode with varying VO2 in insulating and metallic states, respectively. More importantly, the phase modulation is independent in two operating modes, and both cover a 360° cross-polarized phase with efficient polarization conversion. This characteristic makes it obtain arbitrary independent phase information on the metasurface with different modes to switch dual functions dynamically. Here, we experimentally demonstrate the functions of a tunable focal length and large-angle focus deflection of a THz off-axis parabolic mirror to verify the dual-function switching characteristics of the functionally decoupled metasurface. The functionally decoupled metasurface developed in this work broadens the way for the research and application of multifunctional modulation devices in the THz band.

Ga₂O₃ metal–oxide–semiconductor field-effect transistors (MOSFETs) with high-breakdown characteristics were fabricated on a homoepitaxial n-typed β-Ga₂O₃ film, which was grown by metal organic chemical vapor deposition (MOCVD) on an Fe-doped semi-insulating (010) Ga₂O₃ substrate. The structure consisted of a 400 nm unintentionally doped (UID) Ga₂O₃ buffer layer and an 80 nm Si-doped channel layer. A high k HfO₂ gate dielectric film formed by atomic layer deposition was employed to reduce the gate leakage. Moreover, a source-connected field plate was introduced to enhance the breakdown characteristics. The drain saturation current density of the fabricated device reached 101 mA/mm at V_gs of 3 V. The off-state current was as low as 7.1 × 10^-11 A/mm, and the drain current I_ON/I_OFF ratio reached 10⁹. The transistors exhibited three-terminal off-state breakdown voltages of 450 and 550 V, corresponding to gate-to-drain spacing of 4 and 8 μm, respectively.

Ultraviolet (UV) detectors with large photosensitive areas are more advantageous in low-level UV detection applications. In this Letter, high-performance 4H-SiC p-i-n avalanche photodiodes (APDs) with large active area (800 μm diameter) are reported. With the optimized epitaxial structure and device fabrication process, a high multiplication gain of 1.4 × 10⁶ is obtained for the devices at room temperature, and the dark current is as low as ～10 pA at low reverse voltages. In addition, record external quantum efficiency of 85.5% at 274 nm is achieved, which is the highest value for the reported SiC APDs. Furthermore, the rejection ratio of UV to visible light reaches about 10⁴. The excellent performance of our devices indicates a tremendous improvement for large-area SiC APD-based UV detectors. Finally, the UV imaging performance of our fabricated 4H-SiC p-i-n APDs is also demonstrated for system-level applications.

This Letter presents a double-layer structure combining a cracked cross meta-surface and grating surface to realize arbitrary incident linear terahertz (THz) wave polarization conversion. The arbitrary incident linear polarization THz wave will be induced with the same resonant modes in the unit cell, which results in polarization conversion insensitive to the linear polarization angle. Moreover, the zigzag-shaped resonant surface current leads to a strong magnetic resonance between the meta-surface and gratings, which enhances the conversion efficiency. The experimental results show that a more than 70% conversion rate can be achieved under arbitrary linear polarization within a wide frequency band. Moreover, around 0.89 THz nearly perfect polarization conversion is realized.