  We show that by introducing isoelectronic iron (Fe) magnetic impurities and
Beryllium (Be) double-donor atoms into InAs, it is possible to grow a n-type
ferromagnetic semiconductor (FMS) with the ability to control ferromagnetism by
both Fe and independent carrier doping by low-temperature molecular-beam
epitaxy. We demonstrate that (In,Fe)As doped with electrons behaves as an
n-type electron-induced FMS. This achievement opens the way to realize novel
spin-devices such as spin light-emitting diodes or spin field-effect
transistors, as well as helps understand the mechanism of carrier-mediated
ferromagnetism in FMSs.
