Abstract
Germanium/Silicon-Germanium (Ge/SiGe) multiple quantum wells receive great attention for the realization of Si-based optical modulators, photodetectors, and light emitters for short distance optical interconnects on Si chips. Ge quantum wells incorporated between SiGe barriers, allowing a strong electro-absorption mechanism of the quantum-confined Stark effect (QCSE) within telecommunication wavelengths. In this review, we respectively discuss the current state of knowledge and progress of developing optical modulators, photodetectors, and emitters based on Ge/SiGe quantum wells. Key performance parameters, including extinction ratio, optical loss, swing bias voltages, and electric fields, and modulation bandwidth for optical modulators, dark currents, and optical responsivities for photodetectors, and emission characteristics of the structures will be presented.
Highlights
Ge is considered as a material to enhance the performance of Si-based electronic and photonic integrated circuits (IC), with a prospect of high-volume and low-cost manufacturing [1,2,3,4]. being an indirect-gap semiconductor, Ge has strong potential to enable a chip scale Si-based optical interconnect with aggressive requirements in terms of power consumption, data density, and monolithic integration [5]
It is worth mentioning that the reported responsivity and detection speed values from waveguide Ge/SiGe multiple quantum wells (MQWs) photodetectors in Table 2 can be considered improvable as compared to the recent state-of-the-art Ge photodetector [13]
The report of strong quantum-confined Stark effect (QCSE) from the direct-gap transition of Ge/SiGe MQW systems has led to an ambitious quest toward realizing group IV quantum well optical modulators, photodetectors, and emitters from the same material platforms for more than ten years
Summary
Ge is considered as a material to enhance the performance of Si-based electronic and photonic integrated circuits (IC), with a prospect of high-volume and low-cost manufacturing [1,2,3,4]. Bonfanti et al [29] experimentally studied direct-gap related optical transitions in strain-compensated Ge/Si0.15 Ge0.85 MQWs and observed that Ge MQW structures showed optical properties analogous to direct-gap III–V based QWs. In 2010, after the original report in 2005, Chaisakul et al [30] demonstrated QCSE at room temperature from Ge/Si0.15 Ge0.85 MQWs epitaxially grown by low-energy, plasma-enhanced chemical vapor deposition (LEPECVD) [31].
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