Scanning tunnelling microscopy and spectroscopy, plus tight-binding molecular dynamics analyses, provided very strong evidence that the so-called missing-As defect on the (110) surface was an As vacancy in which the neighboring Ga atoms relaxed upwards by about 0.07nm, but did not re-bond. The defect was positively charged and was probably in a 2+ state. It was suggested that the relaxation and preponderance of As vacancies on p-type material was due to the energetics of the defect levels.

G.Lengel, R.Wilkins, G.Brown, M.Weimer, J.Gryko, R.E.Allen: Physical Review Letters, 1994, 72[6], 836-9