  In this work, the thermo-optic coefficient (TOC) of the silicon-rich
amorphous silicon carbide (a-SiC) thin film deposited by plasma-enhanced
chemical vapor deposition is characterized. We found that the TOC of the film
increases as its silicon content increases. A more than three-fold improvement
in the TOC is measured, reaching a TOC as high as $1.88 \times 10^{-4} K^{-1}$,
which is comparable to that of crystalline silicon. An efficient thermo-optic
phase shifter has also been demonstrated by integrating the silicon-rich a-SiC
micro-ring structure with a NiCr heater. Its tuning efficiency $P_{\pi}$ as low
as 4.4 mW has been measured at an optical wavelength of 1550 nm. These findings
make silicon-rich a-SiC a good material candidate for thermo-optic applications
in photonic integrated circuits.
