Identification and quantitative evaluation of compensating Zn-vacancy–donor complexes in ZnSe by positron annihilation

Vacancy defects in epitaxial thin filmCuGaSe2andCuInSe2

“…Similarly, as in Ref. 16 for ZnSe, the results of the calculations show that the positron lifetime of Cu and Ga vacancies is only τ v − τ b = 10-20 ps longer than in the lattice, whereas, for the Se vacancy in the relaxed state 3 and for the divacancy, the lifetime difference is τ v − τ b = 60-80 ps.…”

“…The difficulty in the decomposition is probably due to the presence of a nonvanishing concentration of smaller vacancy defects, which are not dominant trapping centers but affect the spectrum enough to make a proper decomposition impossible. The lifetime in the perfect lattice (called bulk lifetime) in ZnSe is τ b = 240 ps, 16 and since the lattice constants, structure, and the constituent atoms are very similar in ZnSe and CuGaSe 2 , it can also be assumed that τ b ≈ 240 ps in CGS. To get some insight into the vacancy-specific lifetimes, we calculated the positron lifetimes by solving the positron state and constructing the electron density of the wave function of the free atoms, similarly as described in Ref.…”

Defect identification in semiconductors with positron annihilation: Experiment and theory

“…The situation in thin films is clearly better: e.g., p-type ZnSe can be grown by MBE and hence p-n junctions can be fabricated (Park et al, 1990). Vacancy defects on both sublattices have been shown to exist depending on doping in ZnS x Se 1Àx Oila et al, 1999;Desgardin et al, 2000;Gebauer et al, 2002). Cation vacancies complexed with impurities in CdTe and Hg 1Àx Cd x Te have been identified as important defects controlling the conductivity in bulk crystals (Krause, Klimakow et al, 1990;Kauppinen et al, 1997), while both cation vacancies and divacancies have been found in thin films (Liszkay et al, 1994;Keeble et al, 2011).…”

Group-VII point defects in ZnSe

“…Saarinen et al 5 have used positron annihilation spectroscopy to directly identify vacancies in N-doped and Cldoped ZnSe, suggesting that vacancies are involved in the compensation mechanism. A later study by Gebauer et al 6 obtained similar conclusions, attributing the compensation mechanism in n-doped ZnSe to V Zn -donor complexes.…”

“…Equations (6) and (8) form our model for the calculation of defect formation energies. This model will be used in the next section to determine defect formation energies and concentrations.…”