Improvements in the heteroepitaxy of GaAs on Si by incorporating a ZnSe buffer layer

Heteroepitaxy of GaAs on Si with a ZnSe interlayer by low-pressure metalorganic chemical vapor deposition is reported. The structural and electrical properties of the GaAs epilayers grown on ZnSe/Si substrates were found to be superior to those of the GaAs directly on Si. The surface dislocation density of the GaAs/ZnSe/Si film can be reduced to 2×10 ⁵ cm^-2, which is one order of magnitude lower than that of GaAs/Si. The planar Schottky diode fabricated on the GaAs/ZnSe/Si sample shows a reverse breakdown voltage as high as 30 V, whereas the diode on GaAs/Si has a breakdown voltage of about 12 V. In addition, the residual stress in the GaAs heteroepilayers calculated from photoluminescence peak shifts was 8.2×10⁸ dyn/cm² for the GaAs/ZnSe/Si structure, as compared to 2.7×10⁹ dyn/cm² for the GaAs directly on Si. This indicates that the ZnSe intermediate layer is also effective in reducing the residual stress in the GaAs film grown on Si.