Greetings. I am trying to get lower contact resistance in a Hall bar made of a Ge quantum well sandwiched between two SiGe layers. The ohmic metal is Al. After addressing issues like the removal of native oxide and the annealing temperature and atmosphere I still had a relatively high resistance between the contacts.
I saw then the following structure in the paper "Gate-tunable band structure of the LaAlO3-SrTiO3 interface" by A.E.M. Smink (Article Gate-tunable band structure of the LaAlO$_3$-SrTiO$_3$ interface
)My first question is this: what is the purpose of the comb-shaped contacts?
In a discussion with a colleague we discussed the following structure:
The device is built on top of a mesa (yellow). The Al ohmic contacts are displayed in blue and the top-gate in transparent green. Where the top gate overlaps the ohmic contacts the contacts screens the top gate electric field and no charges are induced.. So by making the ohmic contacts into the comb-shape I would hope to increase the frontier were induced charges "touch" the ohmic contacts, reducing the resistance by facilitating the transition of charge from one area to the other. Is this reasoning correct?
Also, each tooth of the comb is like a resistor so the comb is like a parallel association of resistors. Could I decrease the resistance even more by increasing the number teeth on the comb?
Could you suggest me some literature on this kind of structure?
Thank you very much.
Dear Gabriel G. Maia ,
As the contact area of an interface increases its resistance decreases.
However the interface resistance may remain in spite of large area high.
My main advice is to lower the contact resistance by a technique called high low technique. Where you make the surface of the semiconductor heavily doped under the metal contact. In this way you get ohmic metal semicondcutor contact with low resistance. If you material is p-type then you make its surface p+ type.
I would like to follow the paper in the link: Article A. Zekry and G. El-Dllal, “ effect of MS contact on the elec...
You will see as the doping of the semiconductor increases the contact resistance decreases.
If this technique worked please inform us.
Best wishes
you can reduced the resistance by high low technique.and heavily doped under the metal contact.
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