Nitrogen Implanted GaAs as a Promising Photovoltaic Material

As a III-V photovoltaic material, gallium arsenide has promising prospects in aerospace applications and concentrator cells in virtue of its high efficiency, outstanding thermal stability, as well as the resistance to radiation damage.
In order to further increase the efficiency of GaAs based solar cells, one reasonable method is to modify its bandgap thereby the absorption range. A cell with a GaAs base can have several layers of slightly different compositions that allow a cell designer to precisely control the generation and collection of electrons and holes. Alloying is one method to tailor the properties of semiconductor materials for specific applications. The introduction of nitrogen into the GaAs matrix allows to vary the band gap energy in a broad energy range from ~3.4 eV (GaN) to ~0.8 eV (GaN0.15As0.85)1.
Here we present the synthesis of GaNxAs1-x layers using ion implantation and millisecond flash lamp annealing (FLA) techniques. After nitrogen implantation the GaAs wafer is amorphous within the implantation range and N atoms are located mainly in the interstitial position. Post-implantation thermal annealing restores the initial properties of the matrix and leads to the GaNxAs1-x layers formation. The optical properties of the GaNxAs1-x layers were investigated by -Raman spectroscopy, temperature dependence photoluminescence and photoreflectance spectroscopy. It is shown that during milliseconds range FLA nitrogen can be efficiently incorporated into the GaAs matrix. The band gap of nitrogen reach GaAs layer can be easily tuned from 1.34 down to 1 eV by varying the nitrogen fluence and annealing parameters.