Recent advances in artificial intelligence (AI), high-performance computing (HPC), 5G, cloud computing, and the Internet of Things (IoT) are driving unprecedented demands for bandwidth and data throughput [[1], [2], [3]]. Optical interconnect technologies have emerged as solutions to overcome traditional electrical interconnects' inherent bandwidth and power limitations. Wavelength-division multiplexing (WDM), which simultaneously transmits multiple wavelengths over a single optical fiber, is essential for increasing aggregate bandwidth and integration density. As channel count increases in WDM systems, compact and energy-efficient optical modulators become increasingly critical [[4], [5], [6]].

Silicon (Si)-based micro ring resonator modulators (MRMs) have gained considerable attention due to their compact footprint, CMOS compatibility, low power consumption, and high-speed operation, particularly for Co-packed optics [7,8]. However, conventional Si MRMs using lateral or vertical pn junctions exhibit limited modulation efficiency, high insertion loss, and large voltage-length products (Vπ·L). Such limitations stem from the weak free-carrier plasma dispersion effect in Si, requiring higher drive voltages and longer devices to achieve sufficient modulation [[9], [10], [11]].

Recently, semiconductor-insulator-semiconductor capacitor (SISCAP) structures have been proposed as a promising alternative to conventional p–n junction-based modulators. By utilizing carrier accumulation at the semiconductor-insulator interface, SISCAP structures enable improved electro-optic (EO) efficiency and reduced insertion loss [12]. However, despite these advantages, silicon's inherently weak plasma dispersion effect fundamentally limits the achievable modulation depth and bandwidth in Si-based SISCAP modulators. This fundamentally constrains further improvements in voltage-length product (Vπ·L), insertion loss, and signal quality—factors critical for high-density optical interconnects.

To further improve modulation performance, recent studies have introduced various advanced electro-optic materials, such as III-V compound materials [[13], [14], [15], [16]], two-dimensional materials (e.g. graphene [17,18], WSe2 [19,20]), ceramic materials (e.g. BTO [21], LN [22,23], KTN [24]) to overcome Si's inherently weak free-carrier plasma dispersion effect. Among these materials, III-V compound semiconductors have attracted significant interest due to their inherently stronger free-carrier effects and lower optical losses than Si. Integrating III-V materials into SISCAP-based structures can thus significantly enhance electro-optic efficiency and reduce optical losses [13,16]. Recent demonstrations of III-V/Si hybrid modulators have achieved very low Vπ·L values (∼0.07 V cm) and reduced insertion losses (∼16 dB/cm), confirming their suitability for next-generation optical interconnect systems [13]. This paper aims to overcome the limitation of existing Si-based ring modulators by employing SISCAP structure combined with III-V compound semiconductor materials. We perform systematic TCAD and optical simulations to evaluate and optimize the proposed III-V/Si SIS ring modulators for O-band applications. Our investigation specifically targets achieving higher EO efficiency, lower optical losses, reduced operating voltages, and increased modulation bandwidth, providing a practical pathway for implementing compact, efficient, and high-performance WDM optical interconnect systems.