We propose to measure the dynamic nuclear polarization in a GaAs-based structure caused by electrical injection of a spin-polarized current using polarized neutron reflectometry. The nuclear polarization caused by spin polarized electrons has been studied by mainly optical means. Effective magnetic fields of up to 0.4 T have been found. However, the techniques tend to probe the whole depth of the sample. We wish to use polarized neutron reflectometry to obtain a depth profile of the nuclear polarization. The sample proposed is an LED structure in GaAs where the dynamic nuclear polarization from electrical current injection from a 5 nm Fe film can be measured in the quantum well. This will require us to measure at low temperature whilst an electrical current is passed through the sample.