In this review we present our recent progress in growth, characterization and spin properties of ferromagnet/semiconductor heterojunctions that allow electrical spin injection at room temperature. The most promising results were obtained from MnAs/GaAs and Fe3Si/GaAs heterostructures. In addition, the observation of a small out-of-plane magnetization component in MnAs/GaAs(001) heterostructures led to a new promising concept for application in future magnetologic devices. (C) 2004 Elsevier B.V. All rights reserved.