Low-voltage high-speed silicon MOSCAP microring modulator

Silicon microring modulator (Si-MRM) plays an essential role in optical communication and optical computation. Typically, the Si-MRM is modulated by a reversed PN junction that controls the depletion zone width to achieve high-speed operation. A different approach is to drive the Si-MRM with a metal-oxide-semiconductor capacitor (MOSCAP) and utilize accumulated charges to modulate the refractive index. In this work, we demonstrate a Si-MRM with MOSCAP consisting of high mobility transparent conducting oxide (HMTCO)/hafnium oxide insulator/p-type Si, which achieved sub-volt driving voltage and 25Gb/s modulation.