Preparation of thin Ga-doped ZnO layers for core–shell GaP/ZnO nanowires

We studied the formation of a thin ZnO shell deposited by RF sputtering on GaP nanowires, which were grown on GaP(1 1 1)B substrates under vapour–liquid–solid mode by MOVPE. The ZnO layers had the nominal thickness between 10 and 120 nm (measured on planar GaP substrate). The SEM and TEM characterization showed that the ZnO shells fully covered the surface of the NWs from top to bottom. Moreover, a PN junction was created between the nanocrystalline wurtzite ZnO shell and the zinc-blende GaP NW core. The (n)ZnO/(p)GaP PN junction was characterized by I–V characteristics and spectral response measurement. The spectral response showed that the photocurrent was generated mostly the ZnO shell layer and marginally in the GaP material.