Characterization of field-effect mobility at optical frequency by microring resonators

A novel characterization method is proposed to extract the optical frequency field-effect mobility ( μ op , FE ) of transparent conductive oxide (TCO) materials by a tunable silicon microring resonator with a heterogeneously integrated titanium-doped indium oxide ( ITiO ) / SiO 2 / silicon metal–oxide–semiconductor (MOS) capacitor. By operating the microring in the accumulation mode, the quality factor and resonance wavelength shift are measured and subsequently used to derive the μ op , FE in the ultra-thin accumulation layer. Experimental results demonstrate that the μ op , FE of ITiO increases from 25.3 to 38.4 cm 2 ⋅ V − 1 ⋅ s − 1 with increasing gate voltages, which shows a similar trend as that at the electric frequency.