Numerical analysis of Ge/Si hybrid MOS optical modulator operating at mid- infrared wavelength

摘要

We numerically analyze an optical intensity modulator operating at a mid-infrared (MIR) wavelength based on a Ge/Si hybrid metal-oxidesemiconductor (MOS) capacitor formed by bonding a thin Ge membrane on a Si layer. Owing to the large free-carrier absorption of accumulated holes at the Ge MOS interface, the proposed optical modulator is predicted to exhibit efficient absorption modulation of 15 dB mm(-1) with a 2 V amplitude of a gate voltage at a wide MIR spectrum from 2 to 7 mu m. The 250 mu m long device gives an optical modulation amplitude of -3 dBm, which is at least 11 dBm better than that of a Si/Si MOS Mach-Zehnder optical modulator relying on the plasma dispersion effect. The presented analysis shows the usefulness of the free-carrier absorption in Ge for an intensity optical modulator operating at a MIR wavelength. (C) 2019 The Japan Society of Applied Physics