durusmail: mems-talk: GaAs wet etch with Pd/Ge ohmic contact
GaAs wet etch with Pd/Ge ohmic contact
[MEMS talk] sputtering Al2O3
GaAs wet etch with Pd/Ge ohmic contact
Wenting Guo
Dear ALL,

I've currently met a problem related to the wet etch of GaAs/AlAs
(6nm)/GaAs structure.

We have ohmic contacts (Pd/Ge) on the top and the bottom GaAs layer
annealed. They behave well with linear IV curve at room temperature and
with giga ohms at the liquid nitrogen temperature if one contact is at the
bottom while the other on the top.

Then I wet etched (H2O:H2O2;H2SO4=80:8:1) around the ohmic contacts on the
top down to the bottom GaAs while keeping the ohmic contact at the bottom
untouched. Afterwards, I measured the resistance between the top contact
and the bottom contact again. However, the result shows that they are short
through the AlAs layer now.

I tried different combinations of the Pd/Ge thickness (25/75 nm -> 25/15
nm) and the annealing temperature from 350C to 200C. The same short appears
again and again,

Is that possible the wet etchant somehow damage the AlAs layer? I'm running
out of ideas for the moment. Could anyone kindly give me some suggestions
about this?

Many thanks,
Best wishes,
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