Degenerately doped InGaBiAs:Si as a highly conductive and transparent contact material in the infrared range

Abstract

We demonstrate molecular beam epitaxy (MBE) grown degenerately doped InGaBiAs:Si as a new transparent contact material usable from the near-infrared (near-IR) to the mid-infrared (mid-IR). This material system can exhibit high transparency over large portions of the 1.3-12.5 μm wavelength range, with the exact transparency windows determined by the material carrier concentration. As a comparison, the transmittance of the more conventional IR contact material, Indium Tin Oxide (ITO), drops rapidly for wavelengths longer than 1.5 μm. The conductivity of InGaBiAs:Si is also much higher than ITO due to its high doping concentration and good mobility. Our transmission spectra are modeled using a transfer matrix formalism, and the resulting modeled IR transmission spectra closely match our experimental results with proper choice of two fitting parameters, the material plasma frequency and the scattering rate.