Design of low bias voltage Ge/SiGe multiple quantum wells electro-absorption modulator at 1550 nm

Abstract

We design and simulate a Ge/SiGe multiple quantum wells (MQWs) modulator based on quantum confined Stark effect (QCSE) that operates at 1550 nm. By introducing a thick well and thin barrier in multiple quantum wells structure, the compressive strain of the Ge well is reduced and the absorption edge is shifted to the longer wavelength. An 8-band k⋅p model is employed to calculate the eigenstates and absorption spectra, and influences of quantum well parameters on the absorption property is analyzed and discussed. The numerical simulation indicates that the bias voltage is remarkably reduced to 0.5 V with 1 V voltage swing for 10 wells, while still maintaining over 5 dB absorption contrast ratio. The proposed Ge/SiGe modulator can be a potential approach compatible with traditional complementary metal-oxide-semiconductor (CMOS) technology and adoptable for integration with electronic components.

Analysis of Biaxially Tensile Strained Ge/SiGe Multiple Quantum Wells for Electro-Absorption Modulators With Low Polarization Sensitivities

“…The theoretical models used in this calculation, including electronic band structures, polarization dependent absorption coefficient and QCSE of the strained Ge/SiGe MQWs are available in [12], [23]. The parameters are linearly extrapolated, listed in Table 2.…”

Recent Progress on Ge/SiGe Quantum Well Optical Modulators, Detectors, and Emitters for Optical Interconnects

“…For operation within the C-band telecommunication wavelength, although only one Ge/SiGe MQW optical modulator in Table 1 was demonstrated via transmission measurements to have significant optical modulation in the C-band wavelength region [37], C-band QCSE was experimentally demonstrated and theoretically investigated by several researchers. Besides the method of increasing the temperature, C-band QCSE at room temperature was theoretically predicted by reducing the compressive strain in Ge QWs by using a relaxed buffer with a high Ge concentration [23], or decreasing the quantum confinement energy in Ge QWs by using relatively-thick Ge QWs [27,56]. Importantly, C-band QCSE was experimentally demonstrated by Edwards et al [50] and Dumas et al [57] from 14-nm thick Ge QWs via photocurrent measurements.…”

Building blocks of silicon photonics

“…This allows classifying optical modulators in two main groups: (i) Electro-refraction modulators and (ii) Electro-absorption modulators, respectively. The most common physical effects exploited for optical modulation in photonics are Thermo-Optic (TO) [114], Pockels [115][116][117], Franz-Keldysh (FK) [118][119], Quantum confined Stark Effect (QCSE) [120][121][122][123][124][125][126][127], and Free-Carrier Plasma Dispersion effects .…”

“…There are two main EA mechanisms in silicon photonics: the Franz-Keldysh effect and the (QCSE). Both of these effects have been demonstrated in Germanium and Germanium alloys [119][120][121][122][123][124][125][126][127][128], providing a platform for siliconcompatible materials for high speed, low power, and compact modulators.…”

“…The benefits of quantum well structures result from its discrete energy levels thanks to the quantum confinement effect. Some recent demonstrations on high-speed optical modulation have been reported at wavelengths from 1300 nm to 1550 nm [121][122][123][124][125][126][127][128].…”