Dear Orkun,

it is right, its n-type. How thick you suppose to grow the capping layer? Is
5nm enough or will it be still depleted?

With your experience, is the non-reliability of the contacts due to the
difficult local doping upon alloying or is it a surface depletion of the
channel?

My problem with 'higher' doping (5x10^17) was that I could not obtain any
influence of the gate (with 10nm Al2O3 made by ALD). Furthermore, the I-V
characteristics were just linear up to 10V bias, without saturation. So I
was not able to build a MISFET.


@Alinti:

The characteristics of the low doped samples don't look like Schottky, they
are linear near V=0 with a saturation at around 1-2V. The problem is that
the Ohmic region gives me resistivities between Ohm-cm and MOhm-cm(!) on the
same sample separated only some 100Micron apart. The bulk value is around
0.1Ohm-cm.

(Actually, I was not able to fabricate Schottky contacts with any metal I
tried. They are linear with leakage currents around 0.1uA.)


Ciao

Daniel

* Dr. Daniel Grimm
* IFW Dresden
*            - Institute for Integrative Nanosciences -
* E-Mail:    d.grimm@ifw-dresden.de
* Phone: +49 351 4659-314
* Mobile: +49 177 4926561

  _____

From: Oray Orkun Cellek [mailto:cellek@gmail.com]
Sent: Montag, 30. November 2009 20:29
To: D.Grimm@ifw-dresden.de
Subject: Re: [mems-talk] Contacting GaAs



Dear Daniel,

In my experience 1e17 cm-3 doping is too low for reliable and easy GaAs
ohmic contacts.  Assuming it is n-type doping, either add a 1e18 cm-3 doped
cap GaAs layer on top by epitaxy, or increase your RTP temperature, or even
evaporate more In or Ge for more n-type doping...  By the way, check
literature if you have p-type contact.

Orkun
Ankara, Turkey