Understanding Ohmic Junctions with Aluminium and Semiconductors

[Excom]

Hallo

Is there someone that can explain why Al can be used to form Ohmic contats to both p- and n-type Si?

When looking at a Ohmic junction between a metal and a semiconductor, it is formed when the work functions are as follows: $$\Phi_m$$>$$\Phi_p$$ and $$\Phi_m$$<$$\Phi_n$$. How can Al fulfil both or is there something that I am not aware of?

 

[Naty1]

Does this help:

Aluminum is another important contact metal for silicon which can be used with either the n-type or p-type semiconductor. As with other reactive metals, Al contributes to contact formation by consuming the oxygen in the native oxide. Silicides have largely replaced Al in part because the more refractory materials are less prone to diffuse into unintended areas especially during subsequent high-temperature processing.

Wikipedia: http://en.wikipedia.org/wiki/Ohmic_contact#Technologically_important_kinds_of_contacts

 

[Excom]

No it does not help.

I do understand that Al can react with oxygen to form Al2O3 and thereby consum the native oxide. However, this do not explain why Al can make ohmic contact to n- and p-type silicon.