Heterogeneously Integrated Membrane Lasers on Si Substrate for Low Operating Energy Optical Links

• Published in: IEEE journal of selected topics in quantum electronics Vol. 24; no. 1; pp. 1 - 8
• Main Authors: Fujii, Takuro, Takeda, Koji, Diamantopoulos, Nikolaos-Panteleimon, Kanno, Erina, Hasebe, Koichi, Nishi, Hidetaka, Nakao, Ryo, Kakitsuka, Takaaki, Matsuo, Shinji
• Format: Journal Article
• Language: English
• Published: IEEE 01.01.2018
• Subjects: Epitaxial growth; III-V semiconductor materials; Indium phosphide; Quantum well devices; quantum well lasers; semiconductor lasers; Silicon; Substrates; Vertical cavity surface emitting lasers; wafer bonding
• DOI: 10.1109/JSTQE.2017.2778510
• ISSN: 1077-260X

High demand exists for low operating energy optical links that use wavelength division multiplexing technologies in datacenter networks. Thus, we fabricate a directly modulated membrane distributed-reflector laser with low operating energy on a thermally oxidized silicon (Si) substrate. Because we use epitaxial growth to bury an active region on a directly bonded InP-based membrane, it needs to be kept within a critical thickness, which is related to the growth temperature and the thermal expansion coefficients of materials. In previous studies, we used 250-nm-thick structures, causing relatively large series resistance that limited device performance on such aspects as energy cost and output power. In this study, we increase the III-V membrane thickness to 350 nm, which is close to the calculated critical thicknesses. We achieve the same high crystal quality of multiquantum-wells found in our previous studies. The fabricated laser shows a differential resistance of 72 Ω and thermal resistance of 982 K/W. Thanks to a reduction in bias voltage, the laser can be directly modulated at 25.8 Gbit/s with an energy cost of 97 fJ/bit. In addition, due to a reduction in heat generation, direct modulation with a 50-Gbit/s non return to zero signal is demonstrated by increasing bias current up to 10 mA.