850nm IR transmissive electro-absorption modulator using GaAs micromachining

• Published in: Sensors and actuators. A. Physical. Vol. 197; pp. 47 - 52
• Main Authors: Lee, Sang Hun, Park, Chang Young, You, Jang-Woo, Yoon, Heesun, Cho, Yong-Chul, Park, Yong-Hwa
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2013
• Subjects: Electro-absorption modulator; GaAs micromachining; InGaP; IR transmissive device; IR transmissive device; GaAs micromachining; InGaP; Electro-absorption modulator
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2013.04.009

•A new transmissive electro-absorption modulator was proposed and verified.•Epitaxial growth of multi-layer designs was performed by MOCVD process.•Thick InGaP (4λ) layer with a multifunction was grown on the GaAs substrate.•A transmissive structure was realized using GaAs wet etching process.•The experiment verified a high transmittance variation and speed for 3D camera. The paper relates to a transmissive electro-absorption modulator and a method of fabricating the optical modulator for 3D image capturing system. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of high-speed optical shuttering. A 20MHz-switching high speed optical shutter is realized by GaAs based multi-layer design with electro-absorption layers combining with optical resonance cavity and GaAs micromachining based on the etching process. Thick InGaP (4λ) layer was chosen for the transmissive membrane structure and etch-stop of GaAs wet etching. This layer also was n-type doped to enhance the electrical contact resistance. The transmissive window area is divided into 28 cells for a low device capacitance and a high switching speed, and the polyimide layer with low dielectric constant is embedded between p-pad and n-pad to reduce the leakage and parasitic capacitance. As a result, 49.5% of transmittance variation and above 37.7MHz of switching speed are obtained to guarantee the functionality of Time-of-Flight operation of 3D camera.