New Waveguides for Microwave Monolithic Integrated Circuits Using Distributed Parameter Effects of Semiconductor Carriers

单片微波集成电路（mmic）的集成水平目前受到限制，因为无源电路的衬底面积要求很大，尽管有源半导体器件采用细线光刻技术进行了先进的小型化。本文对金属绝缘体半导体和肖特基共面波导在mmic中的应用进行了理论和实验研究。它们形成于具有外延表面层的半绝缘化合物半导体衬底（GaAs和InP）上，由于半导体载流子的分布参数效应，它们表现出显著的慢波传播。这种波导可以减小分布参数无源电路的尺寸。此外，它们的传输特性可以被电偏置改变，从而开辟了电调谐和有趣的非线性相互作用的可能性。建立了MIS和肖特基共面波导的基本设计原理，并采用等效电路的方法对其传输特性进行了理论分析。推导了传输特性与频率和偏置关系的解析表达式。采用分子束外延技术（MBE）在GaAs和InP半绝缘衬底上形成GaAs和InGaAs表面半导体层。结果表明，GaAs肖特基型共面波导具有慢波传输特性，其传输特性与理论预测基本一致。费米能级钉住的控制对于具有偏置调谐能力的MIS共面波导的实际开发显然是极其重要的。本文提出了一种使用超薄MBE硅层的新型钝化技术，该技术在InP上产生了非常有前途的InGaAs MIS结构，而没有任何费米水平钉住的迹象。

The integration level of monolithic microwave integrated circuits (MMICs)is presently limited owing to large substrate area requirements for passive circuitry in spite of the advanced miniaturization of active semiconductor devices with fine-line lithography.In the present study, MIS (metal-insulator-semiconductor) and Schottky coplanar waveguides for application to MMICs are investigated theoretically and experimentally. They are formed on semi-insulating compound semiconductor substrates ( GaAs and InP) with epitaxial surface layers, and show remarkable slow-wave propagation due to distributed parameter effects of semiconductor carriers. Such waveguides can reduce the size of distributed parameter passive circuits. Additionally, their transmission properties can be altered by electrical bias, opening up the possibility of electrical tuning and of interesting non-linear interactions.Basic design principles of MIS and Schottky coplanar waveguides were established and an theoretical analysis of transmission properties was made, using an equivalent circuit approach.Analytical expressions on frequency and bias dependences of transmission properties were derived.Molecular beam epitaxy (MBE) was used to form GaAs and InGaAs surface semiconducting layers on GaAs and InP semi-insulating substrates. The GaAs Schottky-type coplanar waveguides showed slow-wave propagation, and their transmission properties including frequency and bias dependences, were found to be in good agreement with the theoretical prediction.Control of Fermi level pinning is obviously extremely important for practical exploitation of MIS coplanar waveguides with bias tuning capability. A novel passivation technique using an ultra-thin MBE silicon layer was developed, and it resulted in a very promising InGaAs MIS structures on InP without any indication of Fermi level pinning.