Control of tensile strain in germanium waveguides through silicon nitride layers

Abstract

Germanium ridge waveguides can be tensilely strained using silicon nitride thin films as stressors. We show that the strain transfer in germanium depends on the width of the waveguides. Carrier population in the zone center Γ valley can also be significantly increased when the ridges are oriented along the 〈100〉 direction. We demonstrate an uniaxial strain transfer up to 1% observed on the room temperature direct band gap photoluminescence of germanium. The results are supported by 30 band k·p modeling of the electronic structure and the finite element modeling of the strain field.

Extending the emission wavelength of Ge nanopillars to 225 μm using silicon nitride stressors

“…Particularly for the 300 nm pillars, no increase in emission intensity was observed, at variance to various other works [13,16,17]. This is attributed in part to the polarization of the Γ-valley to LH transition.…”

“…As discussed previously, with carrier diffusion throughout the structure, the larger total shift of the spectra, compared to the broadening seen with the 300 nm pillars could be a hallmark of more uniform strain. Strained emission from these samples is more highly red shifted than previous reports using silicon nitride stressor layers [14][15][16][17].…”

“…Optical emission from strained Ge has been demonstrated in a number of ways, for example, with mechanically strained membranes [11], micro-machined structures [12], micro bridge structures [13], and silicon nitride stressor layers applied to Ge microdisks [14,15] and Ge waveguides [16,17]. The use of silicon nitride as a stressor layer is especially interesting, as it is already used in CMOS processes for strained Si channels, and therefore it is of interest to investigate the limits of this approach.…”

Ge-on-Si photonic devices for photonic-electronic integration on a Si platform

“…11(a). Micro-resonators of Ge [45,46,47] and other technologies [48,49] have been examined to enhance the light emission, while the emission enhancement was still less than one order of magnitude. In order to increase the light emission significantly, heavily n-type doping (> 10 19 cm −3 ) in Ge was proposed [50].…”

Strained Ge Light Emitter with Ge on Dual Insulators for Improved Thermal Conduction and Optical Insulation

“…Initial research effort was put into creating thin-film Ge membranes suspended in air, and then transferring external strain via various methods, such as water pressure, gas pressure, and stressor layer [17,[22][23][24][25][26][27][28]. More recently, a few researchers have presented novel structures to induce large tensile strain in Ge, in which a small residual tensile strain in Ge can be greatly amplified due to geometric effects [29][30][31][32].…”