Ageing of aluminum electrical contacts to porous silicon

Electrical contacts to porous silicon (PS) were formed by depositing aluminum onto its surface. The corresponding Al/PS/Si structures show a rectifying behavior, even after prolonged times in contact to the atmosphere. The series resistance and the ideality factor as a function of time of storage in ambient air have been determined by employing a variation of the Norde method. We have also studied the influence of the electrolytic formation parameters in the process of aging of the Al/PS/Si structures. The results show that longer anodization times and higher formation current densities of the PS layer lead to a faster diminution of the current flowing through the Al/PS/Si structure as a result of its exposition to the atmosphere. However, when the surface of the PS layer is chemically etched, the diminution of the current is significantly slower than in the case of untreated samples.