Hello Derek,

I know this problem from our Ga2O3 samples. We use the following method:

First we sputter a titanium layer and second we bond an aluminum wire to the sample (the AL wire contains still a low portion of Si).

Do not use Au (too high work function).

The described procedure gives good ohmic contact. Perhaps it works at your samples.

With Regard

R. Mitdank

Dear Derek Rosdahl,

I don't think you can use the four point probe technique to measure the resistivity of your samples since your samples are semiconductors. Ideally you should use the Hall measurements.

If you are doing annealing at 450 deg C in oxygen environment, then the metal film is oxidized...and you are not going to get proper ohmic contact... either you do annealing in nitrogen environment or deposit metal by using e beam evaporation

Hello Derek,

I do have similar question, any luck with yours?

Plus, I assumed that if I use 4-point probe, contact resistance and type becomes irrelevant, am I wrong?

This image I found from this link seems to explain what I mean:

https://www.ossila.com/pages/sheet-resistance-theory

Same question also seems to be asked here positing what I am asking:

http://four-point-probes.com/questions-and-answers-regarding-resistivity-resistance-surface-resistivity-sheet-resistance-and-volume-resistivity/