Photovoltage spectroscopy is a beneficial technique to investigate the dynamic properties of the spin excitations of ferromagnetic elements fabricated at the surface of a GaAs/〖Al〗_0.33 〖Ga〗_0.67 As heterojunction. This method is of particular interest for probing localized spin wave modes. The high sensitivity of the photovoltage technique arises from the high electron mobility of 2D electrons μ=1.5×〖10〗^6 〖 cm〗^2.V^(-1).S^(-1), which enables efficient rectification of magnetic moment oscillations through the Hall effect. We report on the discrete structure of spin wave eigenmodes as a function of magnetic field orientation, the shape of Co ferromagnets, and the geometry of nanomagnets. We indicated bonding-antibonding spin waves when B_a is parallel to the short side of the stripe at different microwave frequencies at 4K. We also observed Damon-Eshbach modes when B_a is parallel to the stripe. Micromagnetic simulations confirm the experimental results. We observe the discrete structure of the photovoltage for individual dots. We also investigate the effect of the magnetocrystalline anisotropy field of Co on ferromagnetic resonance. Our results demonstrate that photovoltage measurements in hybrid semiconductor-ferromagnetic structures provide a sensitive and extended tool for probing the spin waves of small magnets with a size of 80 nm.