OXYGEN AND TELLURIUM IMPURITIES IN ZINC SELENIDE GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

The properties of 0.6-2.0 mu m thick ZnSe epilayers grown on GaAs (100) substrates by low-pressure metalorganic vapour phase epitaxy (MOVPE) using novel selenium precursors with low cracking temperature have been studied by photoluminescence (PL), secondary ion mass spectrometry (SIMS) and by electrical measurements. It is shown that the luminescence properties of the samples strongly depend on the growth conditions as well as on precursor purity. The concentration of contaminations increased with decreasing growth temperature and exceeded sometimes 10(18) cm(-3), which was higher than the nitrogen dopant concentration in our samples grown at temperatures of about 315 degrees C. The origin of contaminations were precursor impurities. The most effective contaminants are the isovalent column-VI impurities which do not desorb from the surface during growth at low temperatures. We suppose that these impurities can form pairs in the neighbour lattice sites to explain the photoluminescence properties. The current-voltage characteristics exhibit the evidence of p-type conductivity, but the samples remain strongly compensated. Extra pure precursors without group-VI contaminants are necessary to achieve high p-type conductivity by MOVPE.