PIC-integrable, uniformly 056%-tensile strained Ge-on-insulator photodiodes enabled by recessed SiNx stressor

• Main Authors: Lin, Yiding, Ma, Danhao, Lee, Kwang Hong, Wen, Rui-Tao, Syaranamual, Govindo, Kimerling, Lionel, Tan, Chuan Seng, Michel, Jurgen
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Electrical and electronic engineering::Semiconductors; Germanium; Photodetector
• Online Access: https://hdl.handle.net/10356/148609
• Institution: Nanyang Technological University

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 (SiNx) 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 In0.53Ga0.47As 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.