Open AccessNear-Infrared Ge Photodiodes for Si Photonics: Operation Frequency and an Approach for the Future
Author(s) -
Yasuhiko Ishikawa,
Kazumi Wada
Publication year - 2010
Publication title -
ieee photonics journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 73
eISSN - 1943-0655
pISSN - 1943-0647
DOI - 10.1109/jphot.2010.2046026
Subject(s) - engineered materials, dielectrics and plasmas , photonics and electrooptics
Operation frequency is discussed for near-infrared photodiodes (PDs) using Ge layers on Si, which are indispensable for the photonic-electronic convergence on an Si chip. Based on the formula derived from the continuity equation, Ge pin PDs on Si are found to operate with the 3-dB cut-off frequency as high as 80 GHz, which is limited by the slow diffusion current from the n and p layers. In order to increase the frequency, a new structure is examined, which is composed of a p-Ge/i-Si/n-Si heterojunction. In this structure, electrons generated in the p layer of Ge are collected by the i layer of wider gap Si, being similar to uni-traveling-carrier PDs of InGaAs/InP in III-V systems. Reflecting the larger saturation velocity of carriers for i-Si in comparison with i-Ge, higher operation frequencies as large as 100 GHz are expected by optimizing the layer thicknesses.