Pair spectra in copper-doped zinc telluride

The first observation of discrete donor-acceptor pair lines in copper-doped ZnTe is reported. The spectral analysis shows that the two impurities are located on the same sublattice (type-I spectrum) and gives $E_A^{\mathrm{Cu}}+E_D=168\mathrm{}\pm 1$ meV and $\epsilon \simeq 9.15$. The binding energy of the acceptor is obtained from the $n=2\mathrm{}$ orbital states with even and odd parity evidenced from photoexcitation spectra and resonant luminescence of distant pairs. It is deduced that $E_A^{\mathrm{Cu}}\simeq 149$ meV, $E_D\simeq 19$ meV, confirming that the dominant acceptors in ZnTe are Cu atoms on Zn sites and giving direct information on the site occupied by the unidentified shallow donor (s) in this material.