I need to make ohmic contact to the back side of an n-type (~10 ohm-cm)
silicon wafer.  I do not have a convenient way to remove the native oxide
and I do not have the facilities to anneal the wafer.

Can I just evaporate ~200 nm of Au?

I have found comments in the literature about the use of an indium-gallium
alloy, but can find no papers that actually describe technical details like
the alloy ratio, need for an anneal, etc.

Any help would be appreciated.