Characterization of GaAs and Ge Films on (100) Silicon
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CHARACTERIZATION OF GaAs AND Ge FILMS ON (100) SILICON 3.-M. BARIBEAU, D.C. HOUGHTON, P. MAIGNE, W.T. MOORE, R.L.S. DEVINE, M.W. DENHOFF, R.J. STONER, J. McCAFFREY AND T.E. JACKMAN National Research Council Canada, Division of Physics, Ottawa, Canada KIA OR6 ABSTRACT A UHV MBE apparatus in which the deposition of both group IV and group III-V components is possible without breaking vacuum has been utilized to compare the growth of GaAs epilayers on non-polar Si(lO0) and
Ge coated Si(lOO) substrates.
In addition, a comparison of GaAs epilayers
grown on substrates cleaned by ex-situ techniques and on substrates given all UHV in-situ surface preparation was made. Defect reduction by the incorporation of strained-layer superlattice dislocation filters and by post-growth rapid thermal anneal (RTA) thermal cycles was also investigated. Optical and material properties comparable to MBE grown GaAs/GaAs were obtained for GaAs grown on Ge coated Si(lO0) substrates. INTRODUCTION Epitaxial growth of GaAs on Si substrates has attracted considerable attention in recent years [1, 2]. For instance, the monolithic integration of III-V technology with the more mature Si holds promise for high speed or photonic devices complementing conventional Si IC's. The availability of low cost, large diameter Si wafers of high mechanical strength and thermal conductivity is a significant factor driving the development of GaAs/Si. However, considerable problems exist in nucleating the growth of GaAs on non-polar Si surfaces, overcoming the - 4% lattice mismatch and thermal expansign mismatch. Recently there has been considerable success in solving these problems, especially in the utilization of offcut Si(lO0) wafers [3-5] , dislocation filters [3, 5, 6] and postgrowth rapid thermal
annealing (RTA)
[7, 8].
Since Ge and GaAs are lattice matched and have similar thermal expansion coefficients, an alternative approach for obtaining good GaAs on Si would be to deposit an intermediate epitaxial Ge layer on the Si substrate [ 4, 9-11]. This approach makes it possible to separate polar/ nonpolar interface effects from lattice mismatch effects. Recently, the MBE growth of high quality Ge and GexSi x alloys on Si substrates has been demonstrated [12-14]. If no new deýects are created at the GaAs-Ge interface, high quality GaAs can possibly be obtained on Ge coated Si(lO0) substrates. A UHV MBE apparatus in which the deposition of both group IV and group III-V components is possible without breaking vacuum has been utilized to deposit Ge then GaAs on Si substrates to evaluate the usefulness of Ge intermediate layers. In addition success in defect reduction using strained layer dislocation filters and post growth-thermal cycling are demonstrated.
Mat. Res. Soc. Syup. Proc. Vol. 91- 1987 Materials Research Society
176
EXPERIMENTAL All epilayers were grown in a Vacuum Generator V80/V8OH MBE apparatus which has the two separate growth chambers connected by a UHV transfer system. This system has been described in detail elsewhere [10]. Nominal (100)
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