I’m currently working on my graduate thesis on psychoanalysis, and, just as soethe6 and omfgTALIjustIMDu said, psychoanalysis and freudian psychology study the unconscious.
You should also note that the freudian unconscious it’s not the same unconscious that the linguist’s, or even jung’s unconscious, and that acually the idea of “the unconscious” is prior to Freud, but he is the first that linked the unconsciuous to the sexual trieb and repressed memories. If you really want to study the freudian unconscious, you should stick to Sigmund Freud’s work, specially his writings from 1915, that are commonly known as “the metapsychology”:
1. Instincts and Their Vicissitudes (1915)
2. Repression (1915)
3. The Unconscious (1915)
4. A Metapsychological Supplement to the Theory of Dreams (1917 [1915])
5. Mourning and Melancholia (1917 [1915])
The most serious way to read these articles is from the “Standard Edition”, translated by James Strachey. There are lots of other editions and translations, many of them are just pathetic.