The mercury vacancy in Hg1-xCdxTe was not a two-level (as previously supposed), but a three-level acceptor. A third, most shallow (1 to 1.5meV) level (А+ state) appeared due to a capture of a third hole by a neutral acceptor, after the two deeper vacancy levels (A− and А0 states) were already occupied by holes. Due to a capture of non-equilibrium holes by neutral mercury vacancies (under radiation) a positive space charge region arose near an irradiated surface. This caused the anomalies of photo-electromagnetic effect, observed in р-Hg1−xCdxTe at T < 10 to 12K.

Experimental Evidence for the Third Level (А+) of Hg Vacancy in Hg1−xCdxTe. G.A.Shepelskii, M.V.Strikha, S.G.Gassan-Zade: Infrared Physics & Technology, 2012, 55[6], 481-4