POSITRON BEAM PROFILING STUDY OF THE METAL-GAAS INTERFACE

Properties of metal contacts on m-V semiconductors an dependent on the electronegativity of the metal. Generally metals have been classified into three categories according to their behaviour upon heat treatmen t. Au, Ni and W are the three metals belonging to different categories with the descending order of electronegativity. In this study a low e nergy position beam has been used to investigate as-grown Au/GaAs (SI) , Ni/GaAs(SI) and W/GaAs (Sl) samples with different thicknesses of me tal overlayers. The method that has been employed is that of monitorin g the Doppler broadening of annihilation radiation through S parameter measurements as a function of the beam energy. The S-E data were anal ysed by the program VEPFIT with different models and different implant ation profiles. It is found that the interfacial information able to b e extracted from the fitting is limited by present uncertainties in th e implantation profile.