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

Nicolas Ulloa-Castillo, Luis Lastras-Martínez, Raúl Balderas-Navarro, Rafael Herrera-Jasso, and Alfonso Lastras-Martínez.
Applied Physics Letters, Vol. 105(18), pp. 181905. November 2014. , 2014.


In this work we report on photoreflectance (PR) and photoreflectance-difference (PR-D) measurements of GaAs(001) upon deposition of Gd2O3 thin flms. 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 Gd2O3 induces a tensile strain on the GaAs surface and a direct piezo-electric dipole (DPD) 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 E1 and E1+D1 optical transitions.