Unintentionally doped (100) InP wafers were ‘‘cleaned’’ with 12 different etching procedures, either found in the current literature or adapted from Si technology. We present the results of x-ray photoelectron spectroscopy (XPS) and Rutherford backscattering experiments together with electrical properties of Au/InP contacts realized on the same samples. We can distinguish: first, the solutions which result in a rather clean InP surface and give metal-semiconductor Au/InP diodes from those which lead to an approximately 20-Å-thick oxide layer and give metal-insulating-semiconductor structures, and second, the solutions which give electrically stable structures from those which lead to very unstable ones. Detailed electrical measurements [J-V; J(V,T); C(V,T)] have been performed on two kind of stable surfaces: on ‘‘clean’’ etched ones and on one oxidized with NH4OH-H2O2-H2O (5:1:100) solution. For the first ones, a quasi-ideal metal-semiconductor diode is found. For the oxidized surfaces, current flow is controlled by pure tunneling through the oxide layer. A correlation between surface composition evaluated with XPS and surface electrical properties has been clearly established: the electrical properties of the relatively P-rich oxides are quite unstable while the others, In rich, remain stable over several months. The composition and the nature of the various oxides are discussed.

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Use of ultrasound for metal cluster engineering in ion implanted silicon oxide Appl. Phys. Lett. 90, 013118 (2007);

Deep-level transient spectroscopy (DLTS) and neutron-activation analysis have been applied to measure the gold distribution after a phosphorus gettering step. It is found that the gettering mechanism is able to operate without induced dislocations but depends mainly on the surface phosphorus concentration. For example, when Cs=1021/cm3, the gold concentration is reduced by a factor 103 over the whole thickness of a wafer. This Au trapping phenomenon is attributed to the presence of a phosphorus-induced point defect and related to the emitter push effect mechanism.

The formation and identification of binary compounds in Au-InP system has been reported. The contact reaction was investigated in the temperature range 320–360 °C by the combined use of 2-MeV He+ ions backscattering spectrometry, x-ray diffraction, TEM, and SEM. The results give evidence that both In and P form compounds with gold; formation of oxides has not been observed. A model of metallurgical structure of Au/InP contacts annealed at temperatures below or equal to 360 °C has been proposed.