Study of Ge-on-Si Avalanche Photodiodes for Short-Wave Infrared Applications

Abstract Vertical germanium-on-silicon (Ge/Si) avalanche photodiodes offer the advantages of being low-cost, CMOS-compatible and demonstrating high performance for the development of Short-Wave Infrared (SWIR) sensors for telecommunications. Nevertheless, the origins of dark current and noise in Ge-on-Si APDs still need to be clearly identified to improve their performance. In this paper, we report the study of the electro-optical characteristics of fabricated Ge-on-Si Avalanche Photo Diodes. A maximum gain of 95 was achieved at -33 V on these devices (λ = 1550 nm and P = 0.4 mW). Technology Computer-Aided Design (TCAD) simulations were compared with measurements to extract the parameters of the ionization model. Through dark current measurements at various temperatures, we extracted the activation energy at different bias voltages. The dark current is governed by generationrecombination Shockley-Read-Hall (SRH) mechanisms in silicon and germanium below and above the punch-through bias, respectively. Low frequency (LF) noise measurements performed on a 10-µm diameter Ge/Si APD device under dark current conditions showed the presence of a 1/f noise prior to multiplication, confirming a dominant SRH mechanism.