  Studies of spin manipulation in semiconductors has benefited from the
possibility to grow these materials in high quality on top of optically active
III-V systems. The induced electroluminescence in these layered semiconductor
heterostructures has been used for a reliable spin detection. In semiconductors
with strong spin-orbit interaction, the sensitivity of vertical devices may be
insufficient, however, because of the sepration of the spin aligner part and
the spin detection region by one or more heterointerfaces and becuse of the
short spin coherence length. Here we demostrate that higly sensitive spin
detection can be achieved using a lateral arrangement of the spin polarized and
optically active regions. Using our co-planar spin-polarized light emitting
diodes we detect electrical field induced spin generation in a semiconductor
heterojunction two-dimensional hole gas. The polarization results from spin
asymmetric recombination of injected electrons with strongly SO coupled
two-dimensional holes. The possibility to detect magnetized Co particles
deposited on the co-planar diode structure is also demonstrated.
