Structural Characterization of Si0.75Ge0.25 Alloy Layers with Sb/Ge-Mediated Low Temperature-grown Si Buffers

Abstract

SiGe has become a natural choice for the fabrication of low cost and high performance electronic devices. 2000-Å-thick Si0.75Ge0.25 alloy layers were grown on Si (001) substrate using (1 ML Sb)/(∼10 ML Ge)-mediated low temperature-grown Si (LT-Si) buffers by MBE process. After formation of 1 ML Sb on Si (001) a very thin Ge layer (∼10 ML) was grown just before the growth of LT-Si layer, which may be favorable for the creation of strain relaxing dislocation sites. High-resolution X-ray diffraction was used to determine the residual strain in the Si0.75Ge0.25 alloy layers. From the XRD data, it was seen that the residual strain of the alloy layers decreased with decreasing the growth temperature of the LT-Si buffer layers and reached to a lower value of about -0.06% at 300°C. Contact mode AFM observation of the same sample showed a smooth surface with rms roughness of about 13 Å.