THE M-CENTER IN ZINC SELENIDE GROWN BY METALORGANIC CHEMICAL VAPOR-DEPOSITION

The M-centre produces a deep level in ZnSe which is characterized by a distinctive peak in the photoionization spectrum to the valence band, the peak being at 0.83 eV. The centre occurs in most samples of ZnSe whatever the growth method. It can provide the dominant recombination route and therefore can be the limiting factor in the production of efficient blue luminescence at room temperature. Its identity is unclear. We have made photocapacitance measurements on ZnSe epitaxial layers grown by MOCVD. We find that previously published spectra are a superposition of the M-centre spectrum and the spectrum of another centre. The concentration of the M-centre varies with the growth conditions. In the past the carrier mobility and the ratio of near-band-edge to deep-level radiative emission intensity have been used as figures of merit for ZnSe. Our work indicates that the M-centre concentration could be at least as important in material characterization.