Buried Al 0.4 Ga 0.6 A s/G a A s superlattices on Au-GaAs Schottky diodes have been used as an energy filter to study the energetic current distribution in ballistic electron-emission microscopy (BEEM) at room temperature and T= 100 K. Due to the large difference in electron masses in Au and GaAs we find that parallel momentum conservation leads to considerable electron refraction at the Au-GaAs interface. As a consequence, the energetic distribution of the ballistic electron current is inverted beyond the Au-GaAs interface and an almost linear behavior of the BEEM spectrum is observed in the energetic regime of the superlattice miniband.