Surface Properties of Unintentionally Doped GaN Film and ItsContact Behaviour with Ni/Cr/Au Compound Metals

The surface properties of GaN films grown by plasma-assisted molecular beam epitaxy were investigated by using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy, while the depth profile was analysed by the Ar ion sputtering method. The contaminative carbon and silicon are chiefly adsorbed onto the surface while oxygen and aluminum diffuse into the bulk to distribute in a certain depth. The mixture oxides is roughly 0.1μm in thickness. Based on the analytical results of XPS of the GaN films, the Ni/Cr/Au interdigital metal-semiconductor-metal (MSM) structure has been fabricated. It has been found that the contact behaviour of the Ni/Cr/Au/undoped GaN exhibits a linear I-V characteristic under dark and 362-nm light excitation without annealing treatment. The lower resistance of the MSM structure has also been observed.