**4.6.2 Protective and stabilizing properties of fianite films on Ge**

Inorganic dielectric coatings are usually used for passivating and protection of p-n transition surface, as shielding and thermal compensation layer at ion implanting and for interference antireflecting protection. Passivation of the surface is the most important issue for manufacturing ot germanium photodiodes because natural GeO and GeO2 oxides are unstable and, so, can not be considered as the only passivating coatings. It is one feature distinguishing Ge and Si devices (the latter have stable and effective coating of its own SiO2 oxide). This oxide film deposited from a gas phase is of the most frequent use for photodiodes with p+ - n-structure. It has positive charge and by attracting electrons to the surface prevents growth of p-channels thus decreasing probability of generation in the layer. It is worth to note that for improved reliability and stability of characteristics of photodiodes it is necessary to maintain surface state density at 1011 cm-2 eV-1 level. However, this passivating technique is far from ideal because high porosity of SiO2 films that decreases humidity resistance and reliability of the devices.

In order to improve dielectric properties of the protective coating fianite films deposited by magnetron sputtering were used. The opportunity of its application for maintaining highquality practically porous-free protective coating has been confirmed earlier by the experiments.

It has been demonstrated that the use of the fianite protective layer in Ge-structures instead of SiO2 eliminated pulse noise and thus considerably improved photoelectric and performance characteristics of these devices. It has been established that the improvement was related to more uniform nature of the fianite films, in particular, absence of pores, in comparison with SiO2 films, which containing defects in form of pores.
