Optical identification of substitutional acceptors in refined ZnTe

A systematic study of acceptors incorporated by diffusion is carried out on refined melt-grown ZnTe. The properties of five substitutional acceptors are investigated by low-temperature photoluminescence. Since the binding energy of excitons on neutral acceptors is almost unaffected by the central cell potential, the neutral acceptors are identified by the two-hole transitions which give accurate values of acceptor ionization energies. The two dominant acceptors 'b' at 61 MeV and 'a' at 149 MeV are identified as Lisub(Zn) and Cusub(Zn), respectively, while the hole binding energies on Nasub(Zn), Agsub(Zn), and Ausub(Zn) are established as 62.8, 123, and 272 MeV, respectively. These experiments show that all the relatively shallow acceptors involve impurities and not stoichiometric defects. (author)