Student loans are available to PhD candidates. These loans are guaranteed by the government, do not require credit worthiness and are called subsidized and unsubsidized. With subsidized loans, the interest is paid by the government. With unsubsidized loans, the interest accumulates while you are in school, and you will be responsible for paying it. In addition, Grad Plus loans are available, but they do require credit worthiness.
Research grants are available to PhD students who are actively completing research. Many science foundations offer grants and awards based on scientific research. To receive one, you will need to complete a research proposal and application. In addition, arts and sciences foundations offer various grants based on empirical research of various humanities-related endeavors.
Many universities offer fully funded programs that will cover tuition and books while providing a yearly stipend to help cover living expenses. To learn about these programs, visit the university's financial aid website or the website associated with the PhD program to which you are applying. Any program with available funds will automatically offer them to you at the time of acceptance. In exchange for these funds, you will teach undergraduate classes or perform research for selected professors within your program.
There are fellowship funds available to PhD students who are researching particular fields that are of interest to the government. Various agencies, such as the Department of Energy and the Department of Justice, offer funded fellowships in exchange for a research report for or future work with the agencies. Visit the governmental websites associated with your PhD's research-area to obtain information on governmental fellowships and grants for PhD candidates.
Many companies provide tuition assistance and other funds to current or potential employees. These funds may or may not need to be returned, depending on the company and its tuition and education funding guidelines. Some of these programs are competitive and require essays, proof of research and previous awards and achievements.