These are special PhD programs covering selected research fields where funding (part time employment at TU Wien) is provided for doctoral candidates. Most of the doctoral college (German: Doktoratskolleg) have a little bit different requirements than the doctoral programe defined in the curriculum. Offered positions can be found in the bulletin of TU Wien. Doctoral candidates having an employment contract are paid according to the collective bargaining agreement for university staff.
For more information see Funding.