  Here, we propose titanium nitride (TiN) as an alternative plasmonic material
for an on-chip silicon plasmonic Schottky photodetector that is based on an
internal photoemission process and operating at telecom wavelengths. The
examined structure employs an asymmetric metal-semiconductor-metal waveguide
structure with one of the electrodes being gold and the second either gold,
titanium or titanium nitride. Apart from the excellent optical properties
desired for this type of photodetector such as high absorption losses and
reasonably high real part of the permittivity, titanium nitride is a
CMOS-compatible material that enables easy integration with existing CMOS
technology. For the first time, we find a Schottky barrier height of 0.67 eV
for titanium nitride on p-doped silicon, which is very close to the optimal
value of 0.69 eV. This value ensures very high signal-to-noise ratio of the
photodetector operating at a wavelength of 1550 nm. Additionally, TiN provides
shorter penetration depth of the mode into metal compared to Ti, which enhances
transmission probability of hot electrons to a semiconductor and gives rise to
responsivity enhancement.
