PIC-integrable, uniformly tensile-strained Ge-on-insulator photodiodes enabled by recessed SiN_x stressor

Abstract

Mechanical strain engineering has been promising for many integrated photonic applications. However, for the engineering of material electronic bandgap, a trade-off exists between the strain uniformity and the integration compatibility with photonic-integrated circuits (PICs). Herein, we adopted a straightforward recess-type design of silicon nitride (SiN x ) stressor to achieve a uniform strain with enhanced magnitude in the material of interest on PICs. Normal-incidence, uniformly 0.56%-tensile strained germanium (Ge)-on-insulator (GOI) metal-semiconductor-metal photodiodes were demonstrated, using the recessed stressor with 750-MPa tensile stress. The device exhibits a responsivity of 1.84±0.15 A/W at 1,550 nm. The extracted Ge absorption coefficient is enhanced by ~3.2× to 8,340 cm -1 at 1,612 nm and is superior to that of In 0.53 Ga 0.47 As up to 1,630 nm limited by measurement spectrum. Compared to the non-recess strained device, additional absorption coefficient improvement of 10-20% in the C-band and 40-60% in the L-band were observed. This work facilitates the recess-strained GOI photodiodes for free-space PIC applications and paves the way for various (e.g. Ge, GeSn or III-V based) uniformly strained photonic devices on PICs.

Comprehensive material study of Ge grown by aspect ratio trapping on Si substrate

“…Recent study of Ge and GeSn opens a new avenue in IR imaging field. While Ge based devices operate in shortwave-IR (SWIR) range [1,2], the GeSn alloys could extend the operating wavelength to midwave-and longwave-IR (MWIR and LWIR) bands. For example, recently we have reported a set of GeSn mid-IR photodetectors and photoconductors with Sn compositions ranging from 10.5% to 22.3% and cutoff wavelength up to 3.65 µm [3].…”

Design and Optimization of High-Responsivity High-Speed Ge/Si Avalanche Photodiode in the C+L Band

“…Moustafa El Kurdi et al used an omnidirectional SiN stressor to coat Ge microdisk, achieved a biaxial tensile strain of 1.75%, and transformed Ge into a direct bandgap semiconductor [ 18 ]. Besides, Lin Y et al employed a recessed SiN stressor to elevate the tensile strain of Ge to 0.56% in germanium-on-insulator (GOI) metal-semiconductor-metal photodiodes, with an extra 10~60% rise in the absorption coefficient of C+L band [ 19 ].…”