We have examined the compensation processes in nitrogen doped ZnSe grown by molecular beam epitaxy. Two independent donor–acceptor pair emission processes have been observed in photoassisted grown layers and detailed temperature dependence measurements have allowed us to conclude that a deep compensation donor with a binding energy of 44 meV exists in more heavily doped material. We propose that the compensating donor is a complex involving a native defect such as the (VSe-Zn-NSe) single donor and this suggestion is supported by the observation of changes in the carrier concentration profile with time.

Optically detected magnetic resonance has been used to investigate the deep level recombination processes in p-type ZnSe grown by molecular beam epitaxy and doped with nitrogen. In addition to the well-known shallow donor resonance at g=1.11, an anisotropic deep donor resonance is observed with g=1.38 and a deep acceptor resonance is detected at g=2. These results are consistent with the pair recombination processes proposed by us previously where the compensating deep donor was assigned to the VSe-Zn-NSe complex.

The processes involved in the stimulated emission by photopumping in (Zn, Cd)Se-ZnSe multiple quantum wells have been investigated at 77 K for a series of diferent well widths. It has been shown by means of photoluminescence-excitation spectroscopy that the confined excitons in the well play an important role in determining the lasing mechanism. The optical gain just above the lasing threshold is attributed to the recombination of an exciton accompanied by emission of one LO phonon. Far above threshold, inelastic exciton-exciton scattering processes contribute significantly to the gain.

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The interface properties of ZnSe/GaAs heterojunctions grown by molecular beam epitaxy have been studied by electrical methods. The current-voltage and capacitance-voltage characteristics show a hysteresis which can be related to unusually slow current and capacitance transients in response to a change in the reverse bias. We performed admittance spectroscopy measurements at various frequencies in order to investigate this phenomenon. A large frequency dispersion of the capacitance and a broad peak in conductance spectra suggest the presence of interface states at the heterojunction between ZnSe and GaAs. We ascribe the long transients to slow changes in the charge on these interface states. We also propose that interface states result in a voltage-induced lowering of the barrier at the heterointerface. The capacitance versus frequency data were analyzed in terms of Lehovec's model from which the density of interface states of 3 -4ϫ10 12 cm Ϫ2 eV Ϫ1 were calculated.