The book provides an introductory review of the concepts in physics of semiconductor heterostructures (quantum wells) and basic problems in spin transport and spin relaxation. Materials discussed in the book are iron and iron-cobalt as conventional ferromagnets, and III-V semiconductors (GaAs, InGaAs, AlGaAs). A detailed guidance is provided on performing and analyzing spin photodiode experiments, in which spin polarized electrons are created via excitation with circularly polarized light, and transferred across the interface (the spin ejection process). The book also addresses the spin injection process, where a fraction of electrons preserve their spin polarization while tunneling through the Schottky barrier, from the FM into the SC (the spin-LED concept). A supplemental chapter addressing magnetic anisotropy properties of such heterostructures and its active role in the process of spin transport is provided. The book contains 119 relevant figures and 6 appendices addressing experimental techniques in electro- and magneto-optics, numerical modeling and nanofabrication of spin diodes. MS PowerPoint slides are available from the author, for lecture and training preparation.