Improved modulation performance of a silicon p-i-n device by trench isolation

This paper reports on the simulation of the dc and transient performance of a p⁺-i-n⁺ single-mode optical phase modulator suitable for silicon-on-insulator material. An analysis of the variation in the dc and transient performance due to trench isolation has been carried out. The device has been modeled using the two-dimensional device simulation package SILVACO. SILVACO has been employed to investigate the overlap between the injected free carriers in the intrinsic region and the propagating optical mode. On forward bias of the device, free carriers are injected into the intrinsic guiding region of the device, resulting in a change in the refractive index of this region. The device studied is designed to support a single optical mode and is of multimicrometer dimensions, thus simplifying fabrication and allowing efficient coupling to/from single-mode fibers or other single-mode devices. The modeling indicates that increased dc device performance of up to 74% results from a vertical trench defined adjacent to the outer edge of the contact region, as compared to a device without trench isolation. For the same conditions an increase in the transient performance of ~18% is also observed