Bias-free and antenna-coupled CW terahertz array emitter with anomalous Schottky barriers

Abstract

We present a new bias-free antenna-coupled CW terahertz photomixer with interdigitated electrodes. Each finger pair is made of metal/semiconductor/metal (MSM) electrodes with dissimilar Schottky barriers. The two dissimilar metals in each MSM have a barrier height of difference (ΔϕB) and a finite lateral spacing (s). In the proposed teraheretz emitter, not only is the optical absorption and hence photogeneration enhanced by the surface resonant modes, but also the high built-in field increases the terahertz current. Furthermore, by having a large radiation resistance of the antenna integrated to the array electrodes, based on our simulations, it is possible to achieve the maximum power of 35 μW from a dipole antenna coupled to the proposed electrode array with 10 μm ×10 μm active area and pitch of Λ=800 nm. This is more than 196 times larger terahertz power than the highest terahertz power radiated from the array emitters of the same area that contains the bias-free antennaless array of far-field emitters with double pitch size. We have also investigated the limits of thermal breakdown and efficiency degradation of the proposed emitter that play an important role due to the reduction of the active area. Such terahertz sources can pave the way to various biomedical applications such as endoscopic imaging without a need for hazardous external circuitry for biasing, reducing patient health risk.