Design and fabrication of uni-travelling carrier (UTC) photodiode based on InxGa1-xN semiconductors
Résumé
This work is focused both on InxGa1-xN single-layer and InxGa1-xN/GaN multilayered structures, with high Indium content (x>35%). In this study, InGaN/GaN films are epitaxially grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD). The microstructure of GaN and InxGa1-xN thin films are characterized by SEM/AFM/TEM [1] and optically by prism coupling/ ellipsometry for the refractive indices [2]. We focus here on the design and the fabrication of ultra-fast photodiodes operating in visible wavelength range. Different configurations for UTC photodiodes have been fabricated (sizes ranging from 2.5 to 50µm) and the technological processes optimized including dry etching processes for patterning GaN/InGaN layers. Ti/Al/Ni/Au and ITO materials for p and n type contacts are also investigated. [1] A. Gokarna, A. Gauthier-Brun, W. Liu, Y. Androussi, E. Dumont, E. Dogheche, J. H. Teng, S.J. Chua, D. Decoster, Applied Physics Letters ,Vol.96 , Issue: 19, May 2010. [2] A. Gauthier- Brun, J.H. Teng, E. Dogheche, Wei Liu, M Tonouchi A. Gokarna, S.J. Chua, D. Decoster, Properties of InxGa1-xN films in Terahertz range, Applied Physics Letter, 100, 071913 (2012)