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 be en studied by photoluminescence (PL), secondary ion mass spectrometry (SIMS) and by electrical measurements. It is shown that the luminescen ce properties of the samples strongly depend on the growth conditions as well as on precursor purity. The concentration of contaminations in creased with decreasing growth temperature and exceeded sometimes 10(1 8) cm(-3), which was higher than the nitrogen dopant concentration in our samples grown at temperatures of about 315 degrees C. The origin o f contaminations were precursor impurities. The most effective contami nants are the isovalent column-VI impurities which do not desorb from the surface during growth at low temperatures. We suppose that these i mpurities can form pairs in the neighbour lattice sites to explain the photoluminescence properties. The current-voltage characteristics exh ibit the evidence of p-type conductivity, but the samples remain stron gly compensated. Extra pure precursors without group-VI contaminants a re necessary to achieve high p-type conductivity by MOVPE.