Hi All, I'm headed back to the CNF
My first trip there was wildly successful. I sputtered two dots of titanium followed by aluminum on the samples and then evaporated two dots of Al alone.
Table of results: Sample Ti/Al Al only Si-p diode w/anneal ohmic contact Si-n ohmic diode w/anneal Si-int. ohmic (unsure.. I broke it.) Ge-n ohmic ohmic Ge-int ohmic some diode behavior. Poor adhesion.
Samples I-V was done back in Buf. And then samples were annealed up to
300C on a hot plate. Except for the intrinsic Ge the metal adhesion was good. (They all pasted the scotch tape test.) I must say that titanium looks to be a nice metal for contacts.OK after that intro some questions.
I feel I'm reinventing the wheel, I've done a lot of on-line and library reading but there is not very much practical advice for making contacts to semiconductors. (There is a lot of theory.) I keep wondering if there is some old Bell labs technical document that could help me. If anyone knows of anything like that I hope you'll share.
I still would like to make a diode with Ge. Any ideas of a metal to try? Probing the Ge samples with Gold pogo pins it did look like the gold made a rectifying contact. But I'm guessing gold won't stick very well. I thought I'd try Indium.
The Ti/Al metal on Si developed a black layer around the edges. I assume this is oxidation of the Al. And I'm going to try Gold for the top layer.
Finally, are there any other things/ experiments I could make/try by putting down metal on semiconductors? I should add that the diodes displayed a nice photo-response.
Thanks for reading this rather long post.
George H.