In this work, AlxGa1−xAs nanostructures on a planar Si substrate are employed to achieve highly efficient light trapping with improved light absorption. In this context, cylindrical and conical nanostructures are shown to render themselves as better light absorption surfaces. The effects of the AlxGa1−xAs nanostructures geometrical parameters and the Al concentration (x%) on the optical characteristics of the proposed solar absorber (SA) are studied. The optical performance of the suggested SA is numerically simulated using three-dimensional finite difference time domain method. The reported absorber has a superior performance in terms of absorption and short circuit current density, compared to its counterparts in the literature. The SA with cylindrical and truncated cone nanostructures can offer a high short circuit current density of 31.28 and 33.20 mA/cm2, respectively.