Improved MOCVD Growth of GaAs on Si
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IMPROVED MOCVD GROWTH OF GaAs ON Si
R.M. LUM*, J.K. KLINGERT*, B.A. DAVIDSON" AND M.G. LAMONT" AT&T Bell Laboratories, Holmdel, N.J. 07733 **AT&T Bell Laboratories, Murray Hill, N.J. 07974
ABSTRACT In the direct growth of GaAs on Si by MOCVD the overall quality of the heteroepitaxial film is controlled to a large extent by the growth parameters of the initial GaAs buffer layer. We have investigated the structural properties of this layer using Rutherford Backscattering Spectrometry (RBS) and X-ray double crystal diffractometry. The crystallinity of the buffer layer was observed to improve with increasing layer thickness in the range 10-100nim, and then to rapidly degrade for thicker layers. High temperature (750'C) annealing of the buffer layers resulted in considerable reordering of all but the thicker (>200 nm) layers. Alteration of the usual GaAs.Si growth sequence to include an in-situ anneal of the buffer layer after growth interruption yielded GaAs films with improved structural, optical and electrical properties.
INTRODUCTION The MOCVD growth of GaAs directly onto Si substrates without intervening layers is accomplished by using a multi-stage process consisting of an initial pre-growth anneal at 975°C in a flowing hydrogenlarsine ambient followed by a two-step growth sequence[l]. The primary purpose of the high temperature anneal is to remove oxides and other surface contaminants from the Si substrate. In the first growth step a thin GaAs nucleating layer is deposited at low temperatures (
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