Modification of GaAs(001)- β 2 (2x4) surface by Pd-decoration: A DFT study

Photoelectric modification mechanisms of Pd-decoration on GaAs(001)- beta 2 (2 x 4) surface were examined through first-principles calculations based on density functional theory (DFT). Among all purposed Pd-decorated GaAs (001)- beta 2 (2 x 4) models, seven demonstrated have good stability. Due to the adsorption of Pd atoms, band gap and work function of GaAs(001)- beta 2 (2 x 4) surface decreased and further enhanced the photoemission capability of the structure. The evidence showed that the reduced transmission resistance and transmission loss of Pddecorated GaAs(001)- beta 2 (2 x 4) structure were due to the formation of the localized internal polarization field resulted from charge transfer between Pd and GaAs. When electron come across the Pd/GaAs interface, the internal electric field could accelerate electron passing though in just one dimension, which could reduce the interface recombination and enhance interface electron transmission capability. Additionally, Pd-decoration led to a red-shift in the absorption edge and enhanced light adsorption capability in the range of 0.7 to 1.7 eV. The optoelectronic modification effect could be utilized to address the interface transmission losses in multi-junction solar cells, and further optimize the solar cell performance.