Resonant light emission from uniaxially tensile-strained Ge microbridges

• Published in: Japanese Journal of Applied Physics Vol. 57; no. 4S; pp. 4 - 10
• Main Authors: Zhou, Peiji, Xu, Xuejun, Matsushita, Sho, Sawano, Kentarou, Maruizumi, Takuya
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Society of Applied Physics 01.04.2018; Japanese Journal of Applied Physics
• Subjects: Bragg reflectors; Computer simulation; Deduction; Design optimization; Germanium; Holes; Lasers; Light emission; Optical resonators; Photoluminescence; Silicon substrates
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.57.04FH10

A highly strained germanium microbridge is a promising platform for realizing monolithically integrated lasers on a silicon substrate. However, it remains challenging to combine it with optical resonators. Here, we have observed resonant light emission peaks with Q-factors of about 180 in room-temperature photoluminescence spectra from uniaxially tensile-strained germanium microbridges. These peaks are found to correspond to the resonance in Fabry-Perot (FP) cavities formed transversely to the uniaxial stress axis. On the basis of this phenomenon, we design a Fabry-Perot cavity by adding distributed Bragg reflectors (DBRs) laterally to the microbridge. With this design, the optical performance can be optimized without disturbing to the mechanical structure. A Q-factor as high as 1400 is obtained from numerical simulation. Moreover, we prove by theoretical analysis deduction and calculation that the lateral structure will not decrease the strain, unlike the on-pad DBR structure. The structure thus provides a promising solution for the realization of highly strained germanium lasers in the future.