Nonalloyed high temperature ohmic contacts on Te-doped InP

We report on a thermal stability study of WSi0.79 contacts on Te-doped InP. The epitaxial InP layers were grown on Fe-doped semi-insulating InP substrates by metalorganic molecular beam epitaxy. Tri-isopropylindium-di-isopropyltellurium was used as the Te precursor and the doping level was 1.4 x 10(20) cm(-3). Contact metal, amorphous WSi0.79, was sputtered from a composite and an excellent specific contact resistance of 1 x 10(-6) Omega cm(2) was achieved. The specific contact resistivity was also measured at different temperature (25-200 degrees C) and it stayed fair contact. This is clear indication that the current transport through the contact dominates by tunneling. After alloying at temperatures up to 600 degrees C, there is no obvious change of specific contact resistance or sheet resistance. After 700 degrees C annealing, there was significant P out-diffusion detected and the specific contact resistance began to degrade. However, the contact metal morphology and edge definition were unaffected. After 800 degrees C annealing, there was evidence of In out-diffusion after and the surface morphology became rough. (C) 1999 American Institute of Physics. {[}S0003-6951(99)00913-4].