Effects of the low temperature grown buffer layer thickness on the growth of GaAs on Si by MBE

Abstract

The effect of initial low temperature grown buffer (LT buffer) layer thickness on GaAs on Si grown by conventional two-step growth method for molecular beam epitaxy has been investigated. The grown layers have been characterized by photoluminescence (PL), double crystal X-ray diffraction (XRD) and atomic force microscopy (AFM). It is indicated that the crystalline quality and the root-mean-square (RMS) roughness of thick GaAs layer on Si depends on the thickness of initial low temperature grown nucleation buffer layer. The present investigation confirms that the initial layer should be sufficiently thick to obtain good quality smooth layers of GaAs on Si substrate. The FWHM of heavy-hole band emission was as low as 4.8 meV for the samples with initial nucleation layer of around 200 nm. The AFM study revealed that the RMS roughness of the thick GaAs layer on Si is large for the samples with thin initial nucleation layer. Also, the annealed LT buffer layers indicate a similar RMS roughness tendency instead of almost constant RMS roughness for the as-grown LT buffer layers. They suggest that the macroscopic surface morphologies and the film quality of the stressed heteroepitaxial layer are dominated during the heating steps of the initial LT buffer layer.