NIST study accelerates understanding of oxidation mechanisms important to laser manufacturers. (News Briefs).Researchers at NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. have shown that the oxidation kinetics of AlGaAs are independent of semiconductor growth method and edge preparation conditions. Native semiconductor oxide layers are critical components of optoelectronic devices, such as vertical-cavity surface-emitting lasers (VCSEL (Vertical Cavity Surface Emitting Laser) Pronounced "vixel." A type of laser diode that emits light from its surface rather than its edge. A VCSEL's circular beam is easy to couple with a fiber, and due to its surface-emission architecture, can be tested ) used in high-speed data communication, in which they provide optical and electrical confinement. VCSEL manufacturers have reported difficulties with the repeatability of their oxidation process. NIST researchers conducted a study of oxidation rate as a function of relevant semiconductor growth and processing variables for initial AlGaAs layers having Al mole fractions from 0.9 to 1.0. They found that, contrary to the expectations of some device manufacturers, the oxidation rate did not depend on whether the initial layers were grown by molecular beam epitaxy A technique that "grows" atomic-sized layers on a chip rather than creating layers by diffusion. or metalorganic chemical vapor deposition Metalorganic chemical vapor deposition (MOCVD) is a chemical vapor deposition process that uses metalorganic source gases. For instance, MOCVD may use tantalum ethoxide ( (MOCVD MOCVD Metallo Organic Chemical Vapor Deposition MOCVD Metal Oxide Chemical Vapor Deposition ), the two methods most commonly used by the industry. The oxidation was independent of the V/III ratio of the growth, impurity level in the initial epilayer, and specimen edge preparation, whether wet etched, ion milled, chemically-assisted ion-beam etched, or cleaved cleaved (klevd) split or separated, as by cutting. . As expected, the oxidation reaction kinetics were a sensitive function of semiconductor composition, oxidation temperature, and time. The study did reveal, in one sample set grown by MOCVD by an outside laboratory, unintentional fluctuations in the epilayer composition during growth (as confirmed by SIMS analysis), which increased t he oxidation rate. The results of the NIST study are providing VCSEL manufacturers valuable insight into the tolerances of their native oxide fabrication process. They are also important input to a broader investigation of the impact of strain on device reliability. More details can be found in the paper "Comparison of A1GaAs Oxidation in MBE MBE (in Britain) Member of the Order of the British Empire MBE n abbr (BRIT) (= Member of the Order of the British Empire) → tÃtulo ceremonial MBE n abbr (Brit) (= and MOCVD Grown Samples," by Y. Chen et al., Mat. Res. Soc. Symp. Proc. (2002) p. H6.11.1. CONTACT: Alexana Roshko, (303) 497-5420; roshko@boulder.nist.gov. |
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