Structural, morphological, electrical and optical properties of amorphous InxAl1-xN thin films for photovoltaic applications

Abstract

The indium and aluminum nitride (InxAl1-xN) semiconductor material was postulated in 2008 as an excellent candidate to produce solar cells. In this research, amorphous layers of InxAl1-xN (0.55 ≤ x ≤ 0.60) were synthesized using the RF sputtering magnetron technique, and then studied for their possible use in photovoltaic applications. Physical, structural, morphological, optical, and electrical properties were studied. The amorphousness was checked by XRD difractograms. Samples have very smooth surfaces, with very low roughness values, according to AFM and SEM techniques.Electrical properties of the InAlN films were studied using Van Der Pauw technique and Hall Effect parameters. The volumetric carrier concentration decreases when InN fraction mole increases. The mobility values range between 6 × 10−2 and 5 × 10−1 cm2 V−1 s−1, which are lower than those obtained for crystalline and polycrystalline samples. The obtained band gap values could be used in both the absorbing layer and the window layer in solar cells (1.9 eV–2.3 eV). Interestingly, this figures of Eg are very close to the previously obtained values for polycrystalline samples. The optical absorption coefficients were high compared to the materials currently used in solar cells (~105 cm−1). This implies the possibility of using thinner layers in photovoltaic devices based on InxAl1-xN.