Silicon Waveguide Integrated with Germanium Photodetector for a Photonic-Integrated FBG Interrogator.

Hongqiang Li,Shasha Zuo,Zhen Zhang,Ding Zhao,Yaqiang Sun,Sai Zhang,Zanyun Zhang,Shanshan Zhang

doi:10.3390/nano10091683

Abstract

We report a vertically coupled germanium (Ge) waveguide detector integrated on silicon-on-insulator waveguides and an optimized device structure through the analysis of the optical field distribution and absorption efficiency of the device. The photodetector we designed is manufactured by IMEC, and the tests show that the device has good performance. This study theoretically and experimentally explains the structure of Ge PIN and the effect of the photodetector (PD) waveguide parameters on the performance of the device. Simulation and optimization of waveguide detectors with different structures are carried out. The device’s structure, quantum efficiency, spectral response, response current, changes with incident light strength, and dark current of PIN-type Ge waveguide detector are calculated. The test results show that approximately 90% of the light is absorbed by a Ge waveguide with 20 μm Ge length and 500 nm Ge thickness. The quantum efficiency of the PD can reach 90.63%. Under the reverse bias of 1 V, 2 V and 3 V, the detector’s average responsiveness in C-band reached 1.02 A/W, 1.09 A/W and 1.16 A/W and the response time is 200 ns. The dark current is only 3.7 nA at the reverse bias voltage of −1 V. The proposed silicon-based Ge PIN PD is beneficial to the integration of the detector array for photonic integrated arrayed waveguide grating (AWG)-based fiber Bragg grating (FBG) interrogators.

Highlights

Silicon (Si) photonics has been an interesting research topic in recent years due to the potential capability of monolithic integration with complementary-metal-oxide-semiconductor microelectronic circuits [1,2,3]
The fiber Bragg grating (FBG) sensors reflect the optical signals with sensing information back to arrayed waveguide grating (AWG), which distributes the optical signals of different wavelengths to different channels, and converts the optical signals into electrical signals for demodulation through the array of photodetectors (PDs)
The bias setting is performed on the tested samples through the analyzer, under the reverse bias of 1 V, 2 V and 3 V, the detector’s average responsiveness in C-band reached 1.02 A/W, 1.09 A/W and 1.16 A/W

Summary

Introduction

Silicon (Si) photonics has been an interesting research topic in recent years due to the potential capability of monolithic integration with complementary-metal-oxide-semiconductor microelectronic circuits [1,2,3]. We proposed an on-chip arrayed waveguide grating (AWG) interrogator by using the III-V/Si photonic integration technology. The lattice mismatch of group III–V and Si materials is relatively large, which is not conducive to the high-quality monolithic integration of photonic chips. The Ge material in the optical communication band has a higher absorption coefficient and a higher electron and hole mobility in the near infrared band than the group III–V semiconductor. The Ge waveguide detector has achieved progress in terms of bandwidth and responsiveness, many problems must be solved, such as the large dark current of the device and the large lattice mismatch of Si and Ge. a type of Ge material waveguide PD is introduced to realize Si-based monolithic photonic integration. The research simulates and optimizes the waveguide detectors with different structures

Device Structure and Simulation Results

Performance Analysis

Findings

Conclusions