Measurement of the shear strain of the Gd2O3/GaAs(001) interface by photoreflectance difference spectroscopy

摘要

In this work, we report on photoreflectance (PR) and photoreflectance-difference (PR-D) measurements of GaAs(001) upon deposition of GdO thin films. The study is focused on two different substrates: a semi-insulating (SI) with Cr impurities and a Si-doped n-type. PR-D results show that GdO induces a tensile strain on the GaAs surface and a direct piezo-electric dipole is created. Such strain changes the crystal symmetry from cubic to orthorhombic and renders the quadratic electro-optic (QEO) component anisotropic. For the SI substrate, both linear electro-optic (LEO) and QEO components contribute to the PR-D spectrum, whereas the n-type PR-D spectrum is dominated by the LEO component. In both cases, a tensile strain induces a rigid redshift of ∼20 meV to low energies of the E and E + Δ optical transitions.