Radiative and nonradiative rates and deep levels in zinc selenide grown by molecular-beam epitaxy

Abstract

A series of chlorine-doped epitaxial layers of ZnSe have been grown by molecular-beam epitaxy. Measurements have been made of the relative intensity of the blue photoluminescence at room temperature, of the decay time of this emission, and of the concentrations of deep levels determined by photocapacitance techniques. A GaAs buffer layer improves the light emission and decreases the deep-level concentrations. Over the uncompensated donor concentration range 2×1016 to 3×1018 cm−3 the photoluminescence intensity, decay rate, and deep-level concentrations only vary by one order of magnitude. The results are consistent with the room-temperature blue emission resulting in recombination of a free hole with electrons on relatively isolated donors, this radiative recombination competing with a strong nonradiative Hall–Shockley–Read recombination via deep levels in the lower half of the energy gap. The significance of these results for the making of light-emitting diodes and lasers is discussed.