Abstract : High quality growth of ferromagnetic metals/III-V semiconductors heterostructures is an interesting challenge since it allows the integration of the robust magnetism of metals to the semiconductor technology. Nevertheless, the growth conditions of these two materials are totally different, making the growth of hybrid structures quiet complicated (i.e. magnetic tunnel junction). Indeed, at the optimal growth temperature of the III-V SC, the diffusion at the FM/SC III-V interface is very important and result in a rough and undefined interface. In order to prevent diffusion at the MF/SC III-V at the interface, the SC is grown at low temperature. The method results in a SC barrier with a poor quality. The low reactivity and high spin polarization at the MnAs/GaAs interface make this couple of materials a good candidate for FM/SC junctions growth. Recently, MnAs nano-clusters embedded in a GaAs matrix showed quite important magnetoresistance effects. After the MnAs clusters, by annealing a GaMnAs/GaAs(001) layer at high temperature (>400 ◦C), others III-V compounds can be grown on top of it, making this granular layer very attractive for magnetic tunnel junction heterostructures growth. We studied magnetic tunnel junctions MnAs/SC III-V/clusters of MnAs in a GaAs matrix (GaAs:MnAs), which the growth conditions of the bottom electrode (in situ annealing of a GaMnAs layer at T>500 ◦C) can significantly increase the structural and chemical quality of the SC barrier. This work can be divided into three parts. Firstly, the growth conditions of GaAs:MnAs/GaAs(001) and MnAs/GaAs(001) layers have been optimized. Then, original studies of magnetic force microscopy and photoemission spectroscopy (in situ and at the ESRF synchrotron) studies have been carried on MnAs/GaAs(001), GaAs:MnAs/GaAs(001) and GaMnAs/GaAs(001) thin films. This measurements lead to important informations to the elaboration of hybrid structures. Finally, the spin polarized transport through MnAs/SC III-V/GaAs:MnAs junctions has been studied.