Extremely high modulation efficiency IU-V/Si hybrid MOS optical modulator fabricated by direct wafer bonding

We have demonstrated an optical modulator with an InGaAsP/Si hybrid MOS-based phase shifter on Si photonics platform by using direct wafer bonding. Since the electron-induced refractive index change in InGaAsP is much greater than Si, electron accumulation at the InGaAsP MOS interface enables an extremely high modulation efficiency. In conjunction with the void-free direct wafer bonding with ALD Al2O3 bonding interface, we have achieved the superior InGaAsP/Al2O3/Si hybrid MOS interface. Thus, we have successfully fabricated the InGaAsP/Si hybrid MOS optical modulator, exhibiting a modulation efficiency VπL of 0.047 Vcm, approximately 5 times better than that of Si-based MOS optical modulators reported so far even with a similar EOT of 5 nm. Thus, the heterogeneous integration of InGaAsP on Si is effective for significantly improving performance of MOS optical modulators through breaking the inherent trade-off between the EOT scaling and modulation bandwidth.