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

尽管采用细线光刻技术的有源半导体器件已经实现了先进的小型化，但由于无源电路需要大的基板面积，单片微波集成电路（MMIC）的集成度目前仍受到限制。在本研究中，从理论上和实验上研究了应用于MMIC的MIS（金属-绝缘体-半导体）和肖特基共面波导。它们形成在具有外延表面层的半绝缘化合物半导体衬底（GaAs和InP）上，并且由于半导体载流子的分布参数效应而表现出显着的慢波传播。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通过电偏置改变，从而开启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，并使用等效电路方法对传输特性进行了理论分析。推导了传输特性的频率和偏置依赖性的分析表达式。使用分子束外延（MBE）在GaAs和InP半绝缘材料上形成GaAs和InGaAs表面半导体层基材。 GaAs肖特基型共面波导表现出慢波传播，其传输特性（包括频率和偏置依赖性）与理论预测非常吻合。费米能级钉扎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极其重要。开发了一种使用超薄 MBE 硅层的新型钝化技术，它在 InP 上产生了非常有前途的 InGaAs MIS 结构，而没有任何费米能级钉扎的迹象。

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.