A micromachining-based technology for enhancing germanium light emission via tensile strain

Germanium is an attractive material for silicon-compatible optoelectronics, but in its bulk form it does not emit light efficiently because of its indirect bandgap. Applying tensile strain to germanium modifies its band structure such that radiative recombination is enhanced, leading to improved light emission. Here, we introduce the ‘suspension platform for optoelectronics under tension’, a micromachining-based technology that applies large, locally tunable tensile strains to suspended device layers. Using this approach, we demonstrate dramatically enhanced light emission from uniaxially and biaxially tensile-strained germanium-on-insulator device layers. Photoluminescence enhanced by a factor of 130 at a wavelength of 1,550 nm and integrated enhancement by greater than a factor of 260 over bulk germanium are described. The emission exhibits a superlinear dependence on optical pump power. We also report preliminary evidence for enhanced electroluminescence from suspended germanium-on-insulator light-emitting diodes. Scientists employ a micromachining-based technology to achieve significant enhancements in light emission from highly strained germanium-on-insulator samples.