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The change in barrier height caused by sputter metallization of contacts on both GaAs and InP substrates, and using evaporated contacts as a reference, is investigated. It has been found that by annealing, the reference barrier height can be restored. A model is proposed, wherein sputter metallization leads to passivation of interfacial defects by hydrogen. Accordingly, the Fermi level pinning caused by these defects is removed and the barrier height changes and is determined by other mechanisms. Annealing produces a removal of hydrogen and reactivates the amphoteric defects. Additional evidence is given for the assumption that sputter metallization leads to passivation, by hydrogen, of dopants and defects in the semiconductor.

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The electrical characteristics of Ti-pSi metal-oxide-semiconductor diodes have been studied as a function of temperature and of applied voltage, using conventional Schottky barrier capacitance-voltage (C-V) and current-voltage (I-V) measurements. The results show a strong deviation from those expected from thermionic emission and from the minority carrier injection theory for the current mechanism. Unlike other authors who proposed a multistep recombination-tunneling mechanism, we have stressed that a model based on the inhomogeneity of the barrier height over the diode area predicts a temperature and voltage behavior of the I-V characteristic similar to the recombination-tunneling mechanism. The concept of inhomogeneity proposed by former authors is supported by Auger depth concentration profiles which show an intermixed region of Ti and Si. It is observed that the equilibrium semiconductor band bending exhibits a stronger temperature dependence than expected from the variation of the semiconductor Fermi level.

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The heights of CoSi,l-and TiSi,/n-GaAs Schottky barriers are determined, by various methods, to be 0.77 and 0.64 eV respectively. These values are discussed in view of the recently developed Schottky barrier theories such as the advanced unified defect (AUD) model and the effective workfunction (EWF) model. The thermal stability of these contacts is investigated and it is found that t h e CoSi,/n-GaAs barrier height remains reasonably stable up to 600 "C for 10 min anneals and up to 750 "C for 1 min anneals. Under oxygen-free conditions and/or for shorter anneal times, this limit value may probably be increased. Consequently, CoSi, may be an interesting contact material for high-temperature applications such as self-aligned GaAs MESFET fabrication.