The ability to tune resonant frequency in optical microcavities is an essential feature for many applications. Integration of electrical-based tuning as part of the fabrication process has been a key advantage of planar microresonant devices. Until recently, the combination of these features has not been available in devices that operate in the ultrahigh-Q regime where device quality factors ͑Q͒ can exceed 100 million. In this letter, we demonstrate an electrically tunable resonator on a chip

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... th ultrahigh-quality factors. Futhermore, the devices have demonstrated tuning rates in excess of 85 GHz/ V 2 and are capable of tuning more than 300 GHz.