Surface passivation and passivating contacts

For an exploitation of the efficiency potential of thin silicon wafers and films require an excellent surface passivation. The passivation is based on an efficient reduction of interface defect densities and the field effect, whereas the latter reduces the concentration of one charge carrier species at the surface.  

Thermally grown oxides or a silicon nitride layer are usually for this purpose applied. The disadvantages of these layers are on the one side the high process temperature and on the other side the the low passivation quality of SiN for p-type silicon.

As an alternative intrinsic and doped layers as amorphous and nanocrystalline silicon (a-Si:H, a-Si, nc-Si:H) as well as a-SiOX:H, a-SiOXNY:H, a-SiCX:H  as wella s stacks of these layers but also AlOX in dependence of deposition conditions and precursor gases are investigated. Additionally the inclusion of hydrogen depending on the different morphologies are studies. In parallel to the passivating properties these layers have to show suitable optical properties. In particular we focus on the interface between passivating layer and silicon absorber regarding the microscopic explanation of the chemical and the field effect passivation mechanism.