Thanks for the references. I am also seeking the book that contains "Chapter 4" which you can find by Googling "Vacancy formation in n-type silicon-doped GaAs". It has a beautiful table 4.2 that attributes different emission lines to different donors and acceptors. But this fragment on the internet does not say what book it is from and the citations for (Williams 1968; Tajima et al. 1994) are not included.