Creating a new spin-based electronics (often called "spin-electronics" or "spintronics") is one of the hot topics in the current solid-state physics and electronics research. In order to utilize the spin degree of freedom in solids, particularly in semiconductors the current electronics is based on, we need to fabricate appropriate materials, understand the spin-dependent phenomena, and control the spins 1).

In this talk, we will review the recent developments of epitaxial ferromagnetic heterostructures based on semiconductors for spintronics. In particular, we show our magnetotransport study on ferromagnetic III-V semiconductor heterostructures with high Curie temperature (TC). In selectively doped h eterostructures (Mn-delta-doped GaAs / Be-doped AlGaAs), in which holes are supplied from the Bedoped p-AlGaAs layer to the Mn-delta-doped channel, ferromagnetic ordering was clearly observed 2). In the heterostructure prepared with proper conditions, its TC was as high as 172 –250 K, far above the TC of InAs- or GaAs-based random-alloy magnetic semi conductors 3)4). Furthermore, we show the control of ferromagnetism in the heterostructures by using gate electric field and light irradiation at relatively high temperatures (~10 0 K) 5).