Growth of GaP on Si substrates by solid-source molecular beam epitaxy

We report on heteroepitaxial growth of GaP films on 4 degrees tilted (1 0 0 ) Si substrates in a growth temperature interval between 300 degreesC and 7 00 degreesC by solid-source molecular beam epitaxy. Very thin GaP layers (2 -15 ML) were prepared by both MBE and atomic layer epitaxy (ALE) in order t o study the initial nucleation stage. ALE mode of growth has a superior sur face quality in term of its lower rms roughness value. Thick cap layers wer e deposited on the top of a thin GaP buffer grown by ALE. The morphology an d the crystal quality of these layers were investigated by AFM and high res olution XRD. For lower growth temperatures than 400 degreesC, the layers be come amorphous. For 1 mum thick GaP layers, the best rms value was found to be ? nm for the layer grown at 500 degreesC while the best FWHM value obta ined from the rocking curve of (004) plane was 290 arcsec for layers grown at 600 degreesC. This FWHM value is slightly lower than that obtained on Ga P layers grown by MOCVD for the same layer thickness. (C) 2001 Published by Elsevier Science B.V.