Open AccessBandgap-customizable germanium using lithographically determined biaxial tensile strain for silicon-compatible optoelectronics
Author(s) -
David S. Sukhdeo,
Donguk Nam,
Ju-Hyung Kang,
Mark L. Brongersma,
Krishna C. Saraswat
Publication year - 2015
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.23.016740
Subject(s) - germanium , materials science , strain engineering , optoelectronics , photoluminescence , silicon , ultimate tensile strength , photonics , strain (injury) , raman spectroscopy , optics , composite material , medicine , physics
Strain engineering has proven to be vital for germanium-based photonics, in particular light emission. However, applying a large permanent biaxial tensile strain to germanium has been a challenge. We present a simple, CMOS-compatible technique to conveniently induce a large, spatially homogenous strain in circular structures patterned within germanium nanomembranes. Our technique works by concentrating and amplifying a pre-existing small strain into a circular region. Biaxial tensile strains as large as 1.11% are observed by Raman spectroscopy and are further confirmed by photoluminescence measurements, which show enhanced and redshifted light emission from the strained germanium. Our technique allows the amount of biaxial strain to be customized lithographically, allowing the bandgaps of different germanium structures to be independently customized in a single mask process.