Due to the interdisciplinary orientation of the program you can complete the PhD program as Dr. rer. nat. or Dr. phil. In order to participate in the program the PhD supervisor must be a lecturer of ESP. The co-supervisor, on the other hand, does not necessarily have to be a lecturer of ESP.
The degree depends on the thematic focus of the dissertation project, i.e. the field of the PhD-supervisor. Media Informatics and Computational Statistics are completed as Dr. rer. nat; Computer Linguistics, Comparative Linguistics and Phonetics and Speech Processing are completed as Dr. phil.
Please notice the PhD regulations.