Speaker
Description
Highly mismatched alloys (HMAs) – modified semiconductors with an alloying element that has highly different electronegativity from the host semiconductor elements – are used in solar cells and laser diodes due to their highly tunable band gaps. When the alloying element produces a state near the host conduction band (CB), the CB splits into two bands. It was recently shown that HMAs have tunable plasmon resonances spanning the THz to mid-IR range [1]. We evaluate the potential of HMAs for mid-IR plasmonic applications by predicting their bulk plasmon frequency and associated losses.
We characterize the quality of the plasmon resonance at frequency ω using a figure of merit M=|χ|^2⁄(Imχ), which describes the potential of a material to scatter or absorb light, where χ is the electric susceptibility [2]. We develop a theory for the frequency-dependent conductivity, and in turn χ(ω), using a Green’s function method based on the coherent potential approximation [3]. Imχ describes losses in the material, and we use a relaxation time approximation of the conductivity to represent those losses, with scattering times extracted from mobility measurements [4-5] and from model mobilities [6,7].
We find that HMAs doped up to 5×10^19 cm^-3 support a wide range of bulk plasmon frequencies up to approximately 240 meV, with potential to find M competitive with other leading mid-IR plasmonic materials such as doped silicon. We present the mobilities required for HMAs to achieve the quality factors of the highest performing materials.
[1] H. Allami and J. Krich, Phys Rev B 103, 035201 (2021).
[2] O. D. Miller et al., Optics Express 24 3329 (2016).
[3] B. Vélicky, Phys Rev 184, 614 (1969).
[4] J. Ibáñez et al., J Appl Phys 103, 103528 (2008).
[5] K. Volz et al., J Cryst Growth 248, 451 (2003).
[6] W. Walukiewicz et al., Physics and Applications of Dilute Nitrides, Taylor & Francis, 23 (2004).
[7] S. Fahy and E.P. O’Reilly, Appl Phys Lett 83, 3731 (2003).
| Keyword-1 | plasmonics |
|---|---|
| Keyword-2 | highly mismatched alloys |