The magnetoresistance effect have been investigated for junctions consisting of Fe/MgO/n-GaAs/MgO/Fe. RHEED patterns and XRD pole profiles revealed that bottom electrodes, Fe, and inter layers, n-GaAs, grew epitaxially, while that upper electrodes, Fe, grew in a polycrystal form. The magnetoresistance curve correspond to the magnetization alignment between the lower and the upper Fe electrodes was obtained. The junctions exhibit maximum magnetoresistance ratio of 11.7% and 2.8% measured at 5 K and room temperature, respectively. The temperature and applied voltage dependence of resistance and magnetoresistance (MR) ratio were investigated. The MR ratio and resistance in parallel and antiparallel state for upper and lower Fe layer decreased with increasing temperature. It was found that with increasing voltage, MR ratio was maximum when the voltage was around several mV.