  Magnetic $p$-$n$ junction diodes are fabricated to investigate spin-polarized
electron transport. The injection of spin-polarized electrons in a
semiconductor is achieved by driving a current from a ferromagnetic injector
(Fe), into a bulk semiconductor ($n$-GaAs) via schottky contact. For detection,
a diluted magnetic semiconductor ($p$-GaMnAs) layer is used. Clear
magnetoresistance was observed only when a high forward bias was applied across
the $p$-$n$ junction.
