Al_xIn_1-xN on Si (100) Solar Cells (x = 0-0.56) Deposited by RF Sputtering

We investigate the photovoltaic performance of solar cells based on n-Al_xIn_1-xN (x = 0-0.56) on p-Si (100) hetero-junctions deposited by radio frequency sputtering. The Al_xIn_1-xN layers own an optical bandgap absorption edge tuneable from 1.73 eV to 2.56 eV within the Al content range. This increase of Al content results in more resistive layers (≈10^-4-1 Ω·cm) while the residual carrier concentration drops from ~10²¹ to ~10¹⁹ cm^-3. As a result, the top n-contact resistance varies from ≈10^-1 to 1 MΩ for InN to Al_0.56In_0.44N-based devices, respectively. Best results are obtained for devices with 28% Al that exhibit a broad external quantum efficiency covering the full solar spectrum with a maximum of 80% at 750 nm, an open-circuit voltage of 0.39 V, a short-circuit current density of 17.1 mA/cm² and a conversion efficiency of 2.12% under air mass 1.5 global (AM1.5G) illumination (1 sun), rendering them promising for novel low-cost III-nitride on Si photovoltaic devices. For Al contents above 28%, the electrical performance of the structures lessens due to the high top-contact resistivity.