Well, there are actually some great resources already available about this:
https://www.daad.de/en/study-and-research-in-germany/phd-studies-and-research/
https://www.research-in-germany.org/en/jobs-and-careers/info-for-phd-students.html
But I would nevertheless like to summarise this more specifically for you, the person who found this page, because possibly you would like to apply to a PhD with my lab or in a closely-related research field in Germany.
So, what do you need to know? Firstly, there are two main ways you can get a funded PhD position in Germany: either via advertised PhD positions or via a scholarship.
Advertised PhD positions
What do these look like?
Advertised PhD positions are in every respect considered real jobs in Germany, and will be advertised as either 50% or 65% E13 TV-L or TV-H positions, and sometimes as “research assistant” or “research scientist” rather than explicitly as “PhD position”. “TV-L” and “TV-H” refer to the funding system in the government service (https://oeffentlicher-dienst.info/tv-l/); “TV-H” is the payscale specific to the state of Hessen, and there are also some other state-level variants, but these are basically similar. E13 is the primary “researcher” level: full-time postdoc positions are paid 100% E13. The justification for paying PhD students 50% or 65% of the E13 salary is that the remaining time is used to write the PhD thesis/in training-related tasks. An interesting side-effect of this is that a 50% E13 position could also be a half-time postdoctoral position. Another interesting side-effect is that there is no actual requirement for the employee of an E13 50% or 65% position to complete a PhD, so sometimes this will be advertised as an “option”, e.g. “the researcher will have the opportunity to complete a PhD”. Although the majority of these positions are 3 years, it is also possible to see other timeframes advertised (a single year, 4 years etc.) because this is generally dependent on the project funding available rather than on the requirements of the student to graduate. 50% is the default/minimum, but DFG (German Research Council)-funded projects often pay 65% instead.
English, German or both?
Advertising PhD positions in both English and German is common. However, many advertisements will only be in German: in this case, it is likely the researcher is either not interested in attracting international candidates (boo), or needs German-speakers. The latter case can arise if a PhD position is directly funded by a university, rather than by a grant: such university-funded positions often come with a teaching requirement of 2-4 contact hours per week. Depending on the university and the department, German language may be required to teach into the courses currently being offered. In general, most universities in Germany offer a mix of English and German courses, with German dominating at the undergraduate level and MSc courses often being split between English and German, with some offered courses in English only to attract international applicants. In any case, if you don’t speak German it is probably not advisable to apply for a job listing that is only in German!
How do I find these advertisements?
Positions must in general be advertised on the university job listing websites, usually for a minimum of 2 weeks. The problem with directly applying to these positions is that (as with all jobs, even though this is rarely explicitly stated and is definitely not best practice for improving diversity) the person advertising often already has a candidate in mind for the position. As well, the administrative burden of advertising a position is such that it is not an uncommon practice for researchers who are hiring to wait until they find a good candidate, then advertise the position tailored to this candidate. This is by no means a Germany-specific phenomenon, but it is one that candidates should be aware of. Positions which are advertised for longer periods than the minimum are more likely to be casting a broader net for novel applicants rather than to be specifically tailored for a particular person.
Improving your chances
So, how can you improve your chances of getting an advertised position, particularly if these often go to favoured candidates which are already known to the researcher? Actually, given this tendency of researchers to wait and hire specific candidates they think might be good, this makes it very important to target research groups you are extra-interested in with specific emails. Possibly, researchers may have grants under review or other opportunities available to hire that are not yet advertised. Writing a cold-call research email is something that has been extensively covered by other sources, including the links above, but I would reiterate that the most important thing to demonstrate is that you know about and are interested in the research area of the group you are contacting. Read the webpage of the research group, explain why you find this research interesting, and describe what your previous work was on. Proposing topics will usually be a plus, although be aware that for advertised positions the research topic will likely be constrained by the project, so there may not be too much flexibility in this.
What needs to be in the application?
Applying for an advertised position is a little different in Germany than elsewhere. It’s important to meet expectations in this regard, because otherwise your application may not be seriously evaluated. There are two major differences which really count here. The first is that in Germany there is a standard cover letter format for applications (see e.g. https://www.germany-simplified.com/german-cover-letter/; https://www.immigrantspirit.com/perfect-cover-letter-for-germany/ for a general (non-research-specific) overview). Try and follow this convention, although for a PhD position do not worry so much about “what you bring” in terms of skills – if you clearly have experience and interest in the research area this is usually fine. Most researchers won’t expect you to come with a full suite of skills already, this is usually taught during the research period. Maybe this is just a personal preference of mine, but I don’t really take any stated personality attributes that the applicant writes about themselves seriously… I would rather see some information about what you studied, any previous research experience (e.g. the MSc project), and why you think my research is interesting and want to join my group.
The second important thing is that in Germany, it is expected that you provide written reference letters with your formal job application. Can you get away without this, and just write contact details for your references? Maybe, but better not to risk it unless you have to. Two letters are expected (three are fine, but more than that is probably excessive; one is much better than nothing) – they don’t have to be long (1-2 pages seems standard), but for sure should include one from the supervisor of your MSc thesis (or Honours/undergraduate thesis; or both). If you’re not sure if your referee has experience writing these already (most academics will have written these for some reason or other previously, but conventions differ), make sure you are explicit when you ask that this needs to be a formal letter, on institutional letterhead (if possible), and in a pdf or other unalterable document format with a signature from the referee.
Applying for a scholarship (international students)
So what does the scholarship option involve? Fortunately, the DAAD (German academic international exchange service) has this covered, with a lot of information on their website and a comprehensive database of what you can apply for, based on country of origin/residence:
https://www2.daad.de/deutschland/stipendium/datenbank/en/21148-scholarship-database/
Most of these aren’t applicable to domestic (German) students, and usually also not to international students who are already based in Germany. The deadlines vary by country, but there are also contact people per country or region who can help with the applications, as well as a lot of useful information about applying on the website. Make sure to contact any potential supervisor long before the grant application deadline. I would recommend an absolute minimum of two months before the deadline, but anywhere from 3 – 12 months before is pretty much fine, for a yearly deadline. It can take a lot longer to write a proposal than you might think, so don’t leave it until the last minute!
The advantage of having your own scholarship is that you have a lot more options. Most researchers will probably support your application, if you write a good contact email and tell them that this is what you plan, because the money for the scholarship is paid externally, not by the researcher. The project should fit very well to the research group you target though, because experimental reagents are not paid by your scholarship, so ideally you would pick a group which has funded projects you’re already interested in participating in/adding on to. All projects funded by the DFG (German Research Council) are in a public database here: https://gepris.dfg.de/gepris/OCTOPUS?language=en ; some project summaries will be in English and some in German.
Specific formats for scholarship applications vary and should always be checked carefully. Read the instructions, and contact your local scholarship authority representative to make sure everything is clear. Normally the evaluation will be made using a combination of your CV and the project proposal itself.
What are the important things to know about writing a research proposal? This is very similar to writing a grant proposal, for which there is a great deal of information and advice already available online. In brief, clearly state why the research area is important in the introduction (what’s the problem?) then cover what is already known before proposing the specific research question/s you aim to answer which will fill this knowledge gap. Subsequently, provide specific, experimentally testable research objectives and hypotheses, and a detailed experimental research plan you will carry out to test these, including enough information and methodological details that it is clear that these experiments will be achievable (although referencing specific techniques is definitely acceptable). Normally a timeline or Gantt chart is also requested – information on how to prepare these is also findable online, and your prospective supervisor should also be able to advise on approximately how long they think each step will take. Use a reference manager software to save yourself time and prevent the kind of small formatting errors which will make the reviewer lose confidence in your aptitude. There are a number of free ones such as Mendeley.
How do you work out a research proposal question? This can be quite a difficult prospect, and is a lot to ask if you’ve never done it before. In my experience what works best is to have an open back-and-forth discussion with a prospective, interested research supervisor about what you’re interested in. Hopefully, if you pick a supervisor to contact with care, they already have existing projects that you can discuss. The research supervisor should already be very familiar with the literature in the area you are interested in (if they aren’t, consider if this is the best fit for you or if another project or supervisor would work better). So the prospective supervisor may be able to help advise on what research questions are novel and feasible, or may provide a list of directions that they are personally interested in exploring further that you can choose from or build on.
That’s all from me! It took me a while to find most of this out, and I’m sure there are some aspects I’m still unaware of. But I hope it helps applicants applying to do a PhD in Germany.