Intrinsic carrier concentration(ni) is one of the most important physical parameters for understanding the physics of strained Si and Si1-xGex materials as well as for evaluating the electrical properties of Si-based strained devices. Up to now, the report on quantitative results of intrinsic carrier concentration in strained Si and Si1-xGex materials has been still lacking. In this paper, by analyzing the band structure of strained Si and Si1-xGex materials, both the effective densities of the state near the top of valence band and the bottom of conduction band( Nc and Nv) at 218, 330 and 393 K and the intrinsic carrier concentration related to Ge fraction(x) at 300 K were systematically studied within the framework of KP theory and semiconductor physics. It is found that the intrinsic carrier concentration in strained Si(001) and Si1-xGex(001) and(101) materials at 300 K increases significantly with increasing Ge fraction(x), which provides valuable references to understand the Sibased strained device physics and design.
In this paper, we present a novel metasurface design that achieves a high-efficiency ultra-broadband cross polarization conversion. The metasurface is composed of an array of unit resonators, each of which combines an H-shaped structure and two rectangular metallic patches. Different plasmon resonance modes are excited in unit resonators and allow the polarization states to be manipulated. The bandwidth of the cross polarization converter is 82% of the central frequency,covering the range from 15.7 GHz to 37.5 GHz. The conversion efficiency of the innovative new design is higher than 90%.At 14.43 GHz and 40.95 GHz, the linearly polarized incident wave is converted into a circularly polarized wave.
