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When ZnSe is doped p type by the incorporation of nitrogen, a compensation process sets in for effective acceptor concentrations between 10 17 and 10 18 cm Ϫ3 . It is generally agreed that this is due to the creation of compensating donors which have been reported to lie at a depth of about 45 meV. It has previously been shown from optically detected magnetic resonance and spin-flip Raman-scattering experiments that these donors have a gyromagnetic ratio ͑g value͒ of about 1.4, compared with the g value of 1.1 for the more usual shallow donors ͑which lie at about 26 meV͒. We report here a systematic study of a series of ZnSe layers ͑grown by molecular-beam epitaxy͒ in which the nitrogen concentration is gradually increased, and we confirm the correlation between the onset of the compensation ͑at an effective acceptor concentration of about 1.7ϫ10 17 cm Ϫ3 ͒ and the appearance of the 45-meV donor. The spin-flip Raman scattering is a resonance process that requires the laser energy to coincide with the excitonic transition associated with the donor, and we have exploited this effect to determine the difference in the localization energies of excitons bound at the two types of donor. The results show that Haynes's rule is obeyed for donor depths E D extending at least to 45 meV, the exciton localization energy being 0.20E D .

Temperature dependent time-resolved photoluminescence has been used to study the excess carrier recombination in Zn0.75Cd0.25Se/ZnSe single quantum well structures grown by molecular beam epitaxy. For temperatures <100 K radiative excitonic recombination appears to dominate, and the photoluminescence (PL) decay time follows the linear dependence on temperature over the range 50–120 K. At higher temperatures the reduction in PL efficiency and decay time indicate that nonradiative processes associated with the ZnCdSe/ZnSe interfaces dominate the recombination. The results are consistent with theoretical predictions.

The compensating acceptors and donors in nitrogen δ-doped ZnSe epilayers grown by molecular beam epitaxy using a nitrogen rf-plasma source are studied by means of photoluminescence (PL) and photoluminescence excitation spectroscopy (PLE). The temperature dependence of PL and PLE spectra obtained from the nitrogen δ-doped layers is investigated in detail, and a deep acceptor and a deep donor with ionization energies of ∼170 and ∼88 meV are reported for the nitrogen δ-doped layers. These two deep centers are assigned to N clusters, i.e., NSe-Zn-NSe for the deep acceptor and NSe-NZn for the deep donor.

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