Growth and Characterization of Heteroepitaxial GaAs on Semiconductor-on-Insulator and Insulating Substrates
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GROWTH AND CHARACTERIZATION OF HETEROEPITAXIAL GaAs ON SEMICONDUCTOR-ON-INSULATOR AND INSULATING SUBSTRATES
T.P. HUMPHREYS,+
K. DAS,++
N.R. PARIKH,+++
C.A. SUKOW,+ NEMANICH,+ C.J. MINER,+++++ P.L. ROSS+++++ and R.J. MARKUNAS++++ + ++ +++ ++++ +++++
J.B. POSTHILL,++++ R.J. M.K.
SUMMERVILLE,++
Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907 Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599-3255 Research Triangle Institute, Research Triangle Park, North Carolina 27709-2194 Bell-Northern Research Ltd., Ottawa, Ontario K1Y 4H7 Canada
ABSTRACT A systematic study pertaining to the molecular beam epitaxial growth and characterization of GaAs films on various crystallographic orientations of sapphire is presented. For integration with silicon circuitry, heteroepitaxial GaAs layers have also been grown on commercially-available chemical vapor deposited silicon-on-sapphire (SOS) and SOS substrates that have been upgraded by the double solid-phase epitaxy process.
INTRODUCTION To date, the heteroepitaxial growth of GaAs on single crystal silicon substates has been widely studied for the potential monolithic integration of silicon-based VLSI electronic circuits and GaAs optoelectronic devices [1,21. However, it is apparent that the realization of high-quality minority carrier device structures, particularly injection lasers, suffers from the presence of a high density of defects and the formation of microcracks resulting from thermally-induced strain [3]. Consequently, the performance and operating lifetime characteristics of these devices are significantly impaired in comparison to similar optoelectronic structures fabricated on GaAs substrates. In an attempt to address the problem of defect reduction, several approaches, including the use of multilayer heteroepitaxial structures that incorporate either lattice-matched buffer layers or strained-layer superlattices (SLS) have been employed with various degrees of success [4]. However, it has yet to be demonstrated that the application of SLS structures in heteroepitaxial GaAs/Si material systems are effective in achieving the desired dislocation density of - 104 cm-2, which is comparable to homoepitaxial films. The issue of strain reduction is also a very serious and fundamental problem in GaAs/Si heteroepitaxy. Indeed, it has been shown that the presence of thermallyinduced tensile-strain, introduced on post-growth cooling of the composite structure, significantly modifies the optical bandgap and can also result in the formation of cracks in the GaAs epilayer [4,5]. However, it has been recently demonstrated by the present authors that by selecting a sapphire-based material system, in which there is a close match with the thermal expansion coefficient of GaAs, strain-free epitaxial GaAs films can be achieved [6,7]. Moreover, by employing sapphire-based substrat
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