Fully planar room-temperature circulator based on magnetized semiconductors

Abstract

Most nonreciprocal microwave devices use magnetized ferrite materials modeled by a permeability tensor. The performance of such devices starts to degrade above 40 GHz due to the upper limit of the saturation magnetization. Bandwidth and integration into the semiconductor-based MMICs are still issues of concern. The availability of spectrum near the 60–77 GHz range as well as the infrared region has increased the demand for improved performance of devices and systems. Fortunately, advancements in semiconductors technology provide alternative materials for nonreciprocal devices. High mobility semiconductors act like solid-state plasmas, and when exposed to a DC magnetic bias, can be modeled as (gyroelectric) anisotropic material, or magnetoplasma. This gives rise to a permittivity tensor, which might be thought of as the dual to magnetized ferrites. Doped semiconductors like InSb and GaAs are usually employed for this purpose. They can work at higher frequencies; up to THz. Also, the offered bandwidth is huge and well exceeds the available bandwidth of most microwave guiding structures. Being a semiconductor, this material is fully compatible with integration, making it an attractive choice for MMICs applications.