Although the development of a monolithically-integrated, silicon-compatible light source has been traditionally limited by the indirect band gaps of Group IV materials, germanium-tin (Ge_1-xSn_x) is predicted to exhibit direct band gap behavior. In pseudomorphic conditions with materials of smaller lattice constant, the accumulation of compressive strain in Ge_1-xSn_x counteracts this behavior to prevent the direct band gap transition. One possible approach to compensate for this compressive strain is to introduce tensile strain into the system, which can be achieved by applying an external stressing agent to post-fabricated devices. We describe a suspended Ge_0:922Sn_0:078 multiple quantum well microdisk resonator cavity strained by 140 nm of highly compressively stressed silicon nitride. Raman shifts and photoluminescence redshifts indicate that an additional 0.23-0.30% strain can be induced in these microdisks with this approach. The ability to tune the optical performance of these resonator structures by strain engineering has the potential to enable the development of low threshold Ge_1-xSn_x-based lasers on Si.

Date Published: 27 February 2015
PDF: 6 pages
Proc. SPIE 9367, Silicon Photonics X, 93671P (27 February 2015); doi: 10.1117/12.2080146

Published in SPIE Proceedings Vol. 9367:
Silicon Photonics X
Graham T. Reed; Michael R. Watts, Editor(s)