AlGaAs/GaAs Double-Heterostructure Optical Waveguide on Si Substrates
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AlGaAs/GaAs
DOUBLE-HETEROSTRUCTURE OPTICAL ON Si SUBSTRATES
WAVEGUIDE
T. YUASA, M. UMENO, S. SAKAI*, N. WADA** AND Y. UETA* Department of Electrical and Computer Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466, Japan. *Department of Electric and Electronic Engineering, Tokushima University, Minami-josanjima, Tokushima 770, Japan. **on leave from Mastushita Kotobuki Electronic Industries Ltd.
ABSTRACT AlGaAs/GaAs double-heterostructure (DH) optical waveguides on Si substrates which is important in future opto-electric integrated circuits (OEICs) utilizing both Si and GaAs devices is analyzed by the effective index method and fabricated by metalorganic chemical vapor deposition (MOCVD). The structures contain 0.8-pm-thick GaAs guiding layer sandwiched between two 1-pm-thick Al0 . 1Ga0 .9 As cladding layers. All the layers were grown by MOCVD on (100) 2°-off Si substrates by two step method. A top cladding layer was etched leaving 2-pm wide mesa-stripes. The etched depth was changed from 0.65 to 0.90 pm. The field profiles were calculated and measured for 1.3 pm wavelength light. The measured and calculated profiles agree quite well with each other for all the. waveguides having different mesa height. This agreement makes us possible to design more complicated AlGaAs/GaAs waveguides and modulators on Si substrates. .INTRODUCTION Many works have been done for epitaxial growth of AlGaAs or GaAs on Si substrate 1)2). Si as a substrate is superior to GaAs in many cases (ie. hardness, size, thermal conductivity, and cost) . And Si in itself, the technology for IC or LSI has already been'established. On the other hand , AlGaAs and GaAs have larger electron mobilities compared to Si. And they are very good for using as opto-electric devices (because GaAs is direct transition-type semiconductor), especially nonlinior opto- electric devices by AlGaAs/GaAs-MQW are becoming popular. In that meaning, to connect both merits between GaAs and Si is very important. The heteroepitaxial growth of GaAs or AlGaAs on Si is always done by molecular bean epitaxy (MBE) or MOCVD. As the devices on Si, various essential components, such as laser diode (LD) 3 ) , photodiode (PD), field4 effect transistor (FET) ) and photodetector, are reported. Integration these essential components into one chip aiming for opto-electric integrated circuits (OEICs) will be the most important theme in future. For this purpose, the optical waveguides or optical modulators on Si, which monolithically connect the essential optical components on Si are required. The DH-optical waveguide, which is a fundamental structure, is very important for future OEICs. In this paper, we analyzed the near field profiles of DH-optical waveguides by effective index method. 2,EXPERIMrENT All the layers of GaAs/AlGaAs were grown by atmospheric MOCVD. (100) Si substrates oriented 2°off toward [0111 were used. The back of the Si substrates were coated by Si0 2 to avoid Si-autodoping from the back of the Mat. Res. Soc. Symp. Proc. Vol. 228. ©1992 Materi
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