Tensile-strained germanium microdisks

Abstract

We show that a strong tensile strain can be applied to germanium microdisks using silicon nitride stressors. The transferred strain allows one to control the direct band gap emission that is shifted from 1550 nm up to 2000 nm, corresponding to a biaxial tensile strain around 1%. Both Fabry-Perot and whispering gallery modes are evidenced by room temperature photoluminescence measurements. Quality factors up to 1350 and limited by free carrier absorption of the doped layer are observed for the whispering gallery modes. We discuss the strain profile in the microdisks as a function of the disk geometry. These tensile-strained microdisks are promising candidates to achieve Ge laser emission in compact microresonators. V

Analysis of Ge micro-cavities with in-plane tensile strains above 2 %

“…Furthermore, high Qs can potentially be achieved [16], which also serves to reduce the threshold for lasing. Highly strained Ge micro-disks have been demonstrated on GaAs substates [14], and using a double bonding technique to improve the strain uniformity in the vertical direction, which has been shown theoretically to improve gain [6].…”

“…Micro-disks are of significant interest for Ge cavities, as they are compact resonators that allow for high strain transfer due to their undercut profile [14]. Furthermore, high Qs can potentially be achieved [16], which also serves to reduce the threshold for lasing.…”

“…Subsequently, high levels of strain have been demonstrated in micro bridge structures [11], and free standing membranes. Silicon nitride stressors have also been used to demonstrate high levels of strain in waveguides [12], pillar structures [13], and Ge micro-disks [14,15].…”

Lattice strain and tilt mapping in stressed Ge microstructures using X-ray Laue micro-diffraction and rainbow filtering

“…bulge testing) (El Kurdi et al, 2010a;Sánchez-Pérez et al, 2011;Boztug et al, 2013). Strain measurements are usually done by micro-Raman spectroscopy (El Kurdi et al, 2010a;Boztug et al, 2013;Ghrib et al, 2013;Ureña et al, 2013).…”

Direct Bandgap Light Emission from Strained Germanium Nanowires Coupled with High-Q Nanophotonic Cavities

“…However, most reported strainedGe devices exhibit only very slight strains [7,18,19] and could at best provide a minimal reduction in threshold [15,16]. Attempts at inducing higher tensile strains have been made [2,20,21], but have not included a high quality factor (Q) optical cavity and have thus merely exchanged material losses for external optical losses. Similarly, carrier confinement in a double-heterostructure has been explored as an avenue for achieving lasing, but requires complex material growth and is often incompatible with tensile strain [23,24].…”