We demonstrate an electroabsorption modulator on a silicon substrate based on the quantum confined Stark effect in strained germanium quantum wells with silicon-germanium barriers. The peak contrast ratio is 7.3 dB at 1457 nm for a 10 V swing, and exceeds 3 dB from 1441 nm to 1461 nm. The novel side-entry structure employs an asymmetric Fabry-Perot resonator at oblique incidence. Unlike waveguide modulators, the design is insensitive to positional misalignment, maintaining > 3 dB contrast while translating the incident beam 87 mum and 460 mum in orthogonal directions. Since the optical ports are on the substrate edges, the wafer top and bottom are left free for electrical interconnections and thermal management.

An electroabsorption modulator using a side-entry architecture achieved a contrast ratio exceeding 3 dB over a 3.5 nm range in the C-band, using a voltage swing of 1 V and operating at 1008C. Modulation was due to the quantum-confined Stark effect from ten Ge/SiGe quantum wells epitaxially grown on silicon-on-insulator (SOI) wafers. The device exploits an asymmetric Fabry-Perot resonator formed between the totally internally reflecting air-SiGe interface and a frustrated total internal reflection from the buried oxide layer of the SOI substrate.

Photocurrent measurements in Ge quantum wells and quantum tunneling resonance simulations give the first measurements of effective masses and other parameters for design of high-performance SiGe/Ge quantum well optoelectronics on silicon.Germanium is increasingly important for integrating photonics into silicon IC technology. Recent demonstrations of quantum wells (QWs) [1] open many new device possibilities, including highperformance optical modulators based on the quantum-confined Stark effect (QCSE) [2]. Relatively little is, however, known about the key properties needed for QW device design. Here we investigate the shifts of multiple different transitions for the first time in such QWs, fitting experimental photocurrent results with quantum-mechanical tunneling resonance calculations. We give the first experimental characterization of the effective masses and direct bandgaps of Ge and Ge-rich SiGe structures including the effects of strain. Though both Si and Ge are indirect gap materials, the QWs produce the QCSE at the Ge direct bandgap [1]. The measured and simulated QCSE shifts of various different transitions are shown in Fig. 1. By using a relatively large Ge QW width of 22nm, numerous transitions can be seen, corresponding to three confined electron levels and three heavy hole levels. These energy levels and the valence and zonecenter "direct" conduction band energy positions are shown in Fig. 2.

No abstract

No abstract