The development of low noise Schottky diode detector/mixers in the THz region

我们研制了新型低噪声肖特基势垒二极管(SBD)探测器/混合器，用于2.5THz地球大气遥感和4THz高分辨率等离子体诊断。为此，我们主要开发了低损伤ECR等离子体工艺，可以在线监测离子源、电子密度、电子温度、衬底电位和衬底温度。这些数据说明了用Ar/O2等离子体清洗腔体对于提高刻蚀速率的重复性和低损伤刻蚀条件是重要和有效的。其次，我们研制了用于2.5 THz波导混频器的准集成平面SBD(QuIP-SBD)。波导型和波纹型馈电喇叭结构是由英国卢瑟福·阿普尔顿实验室研制的。在2.5THz频率下，获得了16000K(DSB)的混频性能和15.2dB的转换损耗。该混合器目前正在为美国国家航空航天局名为高分辨率动力学肢体探测仪的大气遥感卫星做准备。第三，研究了一种用于4THz高分辨率等离子体诊断的高性能SBD探测器/混合器。为了获得低副瓣辐射方向图，引入了抛物面反射器来代替角形反射器。由于抛物面反射器的焦点可以灵活地设计，通过计算机模拟优化了反射器与晶须之间的间距，从而减小了4THz的旁瓣。新的SBD探测器/混合器结构的制造将于1999年4月完成，并将在国家核聚变科学研究所和中部大学进行测试和测量。

We have developed new low noise Schottky barrier diode (SBD) detector/mixers for 2.5THz earth atmospheric remote sensing and 4THz high-resolution plasma diagnostics.For these purposes, primarily, we have developed low damage ECR plasma process with in-situ monitoring of ion sources, electron density, electron temperature, potential of substrate, and temperature of substrate. These data clarified that chamber cleaning by using Ar/0_2 plasma is important and effective to improve reproducibility of etching rate and low damage etching condition.Secondarily, we have developed Quasi-Integrated Planer SBD (QUIP-SBD) for 2.5THz waveguide mixer. The waveguide and corrugated feedhorn structure have been developed at Rutherford Appleton Laboratory in United Kingdom. The mixer performance of 16,000K (DSB) mixer nose temperature and 15.2dB of conversion loss have been obtained at 2.5THz. The mixer is now preparing for atmospheric remote sensing satellite called High-Resolution Dynamics Limb Sounder at NASA.Thirdly, a high performance SBD detector/mixer for 4THz high-resolution plasma diagnostics has been investigated. A parabolic reflector has been introduced in order to obtain low side lobe radiation pattern instead of a corner reflector. Since a focal point of parabolic reflector can be designed flexibly, spacing between the reflector and the whisker was optimized by using computer simulation, so that the side lobes were reduced at 4THz. Fabrication of the new SBD detector/mixer structure will be completed in Apr. 1999 and it will be tested and measured at National Institute for Fusion Science and Chubu University.