Brewster "mode" in highly doped semiconductor layers: an all-optical technique to monitor doping concentration.

We investigate highly-doped InAsSb layers lattice matched onto GaSb substrates by angular-dependent reflectance. A resonant dip is evidenced near the plasma frequency of thin layers. Based on Fresnel coefficient in the case of transverse electromagnetic wave, we interpret this resonance as due to the excitation of a leaky electromagnetic mode, the Brewster "mode", propagating in the metallic layer deposited on a dielectric material. Potential interest of this mode for in situ monitoring during device fabrication is also discussed.