Abstract: Although lasing is meanwhile achieved in various ZnSe based heterostructures, the underlying mechanism is still seriously under debate. We measured the gain spectra of various MOVPE and MBE grown samples using the variable-stripe-length method. A description of the gain spectra for low particle densities is possible in terms of the model of Ding et al. The responsible gain mechanism is assumed to be an induced recombination of strongly exchange- interacting localized excitons. Predictions and limitations of the model are discussed for various temperatures, exciton densities, excitation conditions and sample designs. However, several indications are given that under certain circumstances more than one process contribute to lasing, in particular biexciton recombination seems involved in the gain mechanism. Electron-hole plasma recombination is only important for extremely high excitation densities which are not aspired for injection laser diodes based on II-VI materials. This is in strict contrast to the III-V lasers, where the electron-hole plasma recombination is the dominant lasing process.!19
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