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EFFECTS OF THE SELENIUM PRECURSOR ON THE GROWTH OF ZnSe BY METALORGANIC CHEMICAL VAPOR DEPOSITION KONSTANTINOS P. GIAPIS, LU DA-CHENG, AND KLAVS F. JENSEN Department of Chemical Engineering and Materials Science University of Minnesota, Minneapolis, MN 55455 ABSTRACT The growth of ZnSe on GaAs substrates by metalorganic chemical vapor deposition was investigated in a specially designed vertical downflow reactor. Dimethylzinc was used as the Zn source while different Se source compounds (hydrogen selenide (H2Se), diethylselenide and methylallylselenide) were employed to determine the effect of different source combinations on morphology, thickness uniformity, growth rate, electrical properties and photoluminescence (PL) characteristics of the grown ZnSe films. The H2 Se was produced in situ by reaction of H2 and Se followed by distillation to control the amount of H2Se entering the reaction zone. H2 Se produced very high mobility films with good PL spectra but poor surface morphology. Diethylselenide led to layers of good morphology and PL characteristics but the films were highly resistive. Unusual surface features were observed for methylallylselenide. INTRODUCTION High quality epitaxial layers of ZnSe, that can be doped controllably, have a well-recognized potential use in blue light emitting diodes and injection lasers. Metalorganic chemical vapor deposition (MOCVD) is a promising technique for reproducible growth of high purity ZnSe films. Different source compounds have been investigated over the past 10 years to improve material properties and to gain insight into the underlying growth chemistry. It was recognized early that the use of hydrogen selenide (H2 Se) with zinc alkyls led to premature gas phase reactions, resulting in poor film morphology, thickness uniformity, and inefficient source utilization [1,2]. This fact, in combination with the high toxicity of H2 Se has led to investigations of alternative organometallic Se sources [3-7]. In this paper, three different selenium sources: H2 Se, diethylselenide (DESe), and the new methylallylselenide (MASe) are investigated. ZnSe films, grown by MOCVD with dimethylzinc (DMZn) as the common Zn source, are evaluated by their morphology, thickness uniformity, growth rate, electrical properties and photoluminescence characteristics. The results are reported in terms of the best material grown at optimal conditions for each source combination. EXPERIMENTAL The ZnSe films were grown in a loadlock-equipped, vertical stagnation point flow MOCVD reactor. A mass spectrometer system, with a sampling port immediately downstream of the susceptor, was used to monitor stable reaction by-products. DMZn (Texas Alkyls) was used as the Zn source while three different Se sources were tried: MASe (American Cyanamid), DESe (Alfa Products) and H2 Se. The H2 Se was produced in-situ from Pd-purified hydrogen and 99.9999 % pure selenium (Osaka Asahi Metals) in a small reactor unit, separated from selenium and partially condensed, so that a controlled amount of H2 Se in H2 could be in