The effect of substrate misorientation on atomic ordering in Ga_(0.52)In_(0.48)P epilayers grown on GaAs (001) substrates by Gas-Source MBE

摘要

The ternary III-V semiconductor Ga_(0.52)In_(0.48)P grown on GaAs substrate has been studied for visible wavelength light sources for information processing, laser printing and compact disk systems. In epilayers grown by MOCVD or Solid Source MBE, optical emission with reduced energy is known to originate from atomic ordering of the alloy and the degree of ordering of the group III elements has been found to be significantly influenced by the degree of substrate misorientation from (001). This paper reports a Transmission Electron Microscopy (TEM) study conducted on Ga_(0.52)In_(0.48)P epilayers grown on misoriented (001) GaAs substrates by Gas-Source Molecular Beam Epitaxy. For a growth temperature of 530 deg C, substrate off-cut angles of 0deg, 7deg, 10deg and 15deg towards (111)A were investigated. Selected Area Diffraction Patterns obtained, indicated that the antiphase domain size decreases with increasing off-cut. TEM results have been correlated with band gap measurements obtained from PL and PLE spectra. The band gaps of Ga_(0.52)In_(0.48)P epilayers grown by GS-MBE were found to be larger than those of the same composition grown by MOCVD or Solid Source MBE. This indicates potential for laser devices of shorter wavelengths.