Group-IV midinfrared plasmonics

Abstract

Abstract. The use of heavily doped semiconductors to achieve plasma frequencies in the mid-IR has been recently proposed as a promising way to obtain high-quality and tunable plasmonic materials. We introduce a plasmonic platform based on epitaxial n-type Ge grown on standard Si wafers by means of low-energy plasma-enhanced chemical vapor deposition. Due to the large carrier concentration achieved with P dopants and to the compatibility with the existing CMOS technology, SiGe plasmonics hold promises for mid-IR applications in optoelectronics, IR detection, sensing, and light harvesting. As a representative example, we show simulations of mid-IR plasmonic waveguides based on the experimentally retrieved dielectric constants of the grown materials. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Mid-infrared n-Ge on Si plasmonic based microbolometer sensors

“…The decrease in the wavelength (increase in the wavenumber) of the plasmon edge as the doping density increased for n-Ge epilayers of thicknesses between 600 nm and 1000 nm [2][4] [5] is demonstrated in Fig. 1.…”

“…where N is the doping density, m * is the effective mass, ǫ 0 is the permittivity of free space, ǫ ∞ is the high frequency dielectric constant, q is the electron charge, c is the speed of light and λ is the wavelength [2]. In the visible, metals such as Au and Ag can be used but these are incompatible with silicon foundries due to fast diffusion and deep level trap states.…”

n-Ge on Si for mid-infrared plasmonic sensors

“…Fig. 1 demonstrates the increase in the wavenumber (decrease in wavelength) of the plasmon edge as the doping density increased for n-Ge epilayers of thicknesses between 600 nm and 1000 nm [2][4] [5]. The lowest wavelength of ∼ 3.1 µm was achieved for an activated doping density of 2.1×10 20 cm −3 at 300 K. This is sufficient to enable electron beam lithography and reactive ion etching from the 1000 nm thick n-Ge material [4] into arrays over a 5 × 5 mm 2 array.…”

“…Plasmonic materials [1] have the free electron oscillations in a metal coupled to photons and allow near field amplification of radiation below the plasmon edge [2] defined in wavenumbers ( …”

Mid-Infrared Sensing Using Heavily Doped Germanium Plasmonics on Silicon Substrates

“…An alternative to metals that has been suggested is to use highly doped semiconductors [3][4]. Nominally un-doped semiconductors usually have a plasma frequency in the far-infrared [5], whereas doping levels ≥ 10 19 cm -3 are required for the MIR [1].…”