Non-Hydride Group V Sources for Omvpe
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NON-HYDRIDE GROUP V SOURCES FOR OMVPE
G.B. Stringfellow Departments of Materials Science and Engineering and Electrical Engineering University of Utah, Salt Lake City, Utah 84112
ABSTRACT A major limitation to the continuing development of organometallic vapor phase epitaxy (OMVPE) for the growth of II/V semiconductor materials is the hazard posed by the hydride sources, AsH3 and PH 3, which are virtually universally used, in high pressure cylinders, as the group V source materials for the growth of the highest quality materials. The set of stringent requirements for an organometallic group V source, which includes a high vapor pressure (>50 Torr) and freedom from undesirable carbon contamination, eliminates most commonly available non-hydride group V sources. Recent research on newly developed sources has shown considerable promise. The entire area of group V sources, including the elemental sources, for OMVPE growth of II/V materials will be reviewed. The sources with no hydrogen atoms attached to the group V atom, the elemental, trimethyl-V, and triethyl-V, sources all appear to give unacceptably high carbon incorporation, as does dimethylarsine. Diethylarsine, which has one H attached to the As, produces high quality GaAs. Tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP) appear to be promising source materials. TBP has a very low toxicity, a vapor pressure ideal for OMVPE growth, and the pyrolysis occurs at lower temperatures than for PH 3. No carbon contamination can be attributed to the TBP. Control of the As/P ratio in OMVPE grown GaAsP is much improved for TBP as compared with PH 3 due to the more rapid pyrolysis. TBAs has similar attributes including a favorable vapor pressure and lower pyrolysis temperature than AsH3. The substitution of TBAs for AsH3 results in no observable increase in carbon in the epitaxial GaAs. Phenylarsine is a similar source, with a phenyl radical substituted for a single H atom on AsH3. The vapor pressure of phenylarsine is quite low and the pyrolysis temperature is expected to be some what lower than that for AsH 3. Limited results indicate that carbon incorporation in GaAs is acceptable only when TEGa is the group V source.
INTRODUCTION Organometallic vapor phase epitaxy (OMVPE) is a technique for the growth of materials, including the Ill/V semiconductors, using volatile organometallic compounds to transport the nutrients to the growing solid/vapor interface. Typically the trimethyl- or triethyl-group III elements, TMGa, TMIn, TMAI, TEGa, TEIn, and TEAl, are used in combination with the group V hydrides, AsH3 and PH3 . Historically, the hydrides have been used because of their ready availibility at relatively high purity levels. During the last decade OMVPE has advanced to such a degree that it is today considered the leading technique for commercial production of IIl/V semiconducting materials and structures for most device applications. This is because OMVPE has been demonstrated to fulfill the most stringent requirements for the most advanced devices, includin
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