Alternative Group V Precursors for the Growth of Al-Based III-V Epitaxial Layers by OMVPE
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ALTERNATIVE GROUP V PRECURSORS FOR THE GROWTH OF Al-BASED Ill-V EPITAXIAL LAYERS BY OMVPE
W. S. HOBSON* AND M. GEVA** "AT&TBell Laboratories, Murray Hill, New Jersey 07974 **AT&T Bell Laboratories, Breinigsville, Pennsylvania 18031
ABSTRACT Tertiarybutylarsine (TBAs), tris-dimethylaminoarsenic (DMAA), and tertiarybutylphosphine (TBP) were investigated as alternatives to arsine and phosphine for the growth of AIGaAs, AllnAs, and AlInP by organometallic vapor phase epitaxy. The use of TBAs led to a significant reduction in carbon and oxygen incorporation compared to AsH 3 for AlGaAs. Increasing the TBAs molar flow rate reduced the oxygen (and carbon) concentration. Lower oxygen concentration was observed in AIInP grown with TBP compared to PH 3 . Increasing the PH 3 molar flow rate decreased the oxygen incorporation in AlInP. The morphology of AIInP improved considerably as the growth temperature was increased from 650°C to 750'C, similar to the case of PH 3 . AlInAs and AIGaAs layers grown with DMAA exhibited rough morphology, presumably due to oxygen-containing impurities in the DMAA source. INTRODUCTION There is significant interest in new precursors for organometallic vapor phase epitaxy (OMVPE) and metalorganic molecular beam epitaxy (MOMBE). Motivations include improving process safety, reducing impurity incorporation, lowering the growth temperature, and increasing the efficiency of the reactants. Of particular importance is the replacement of the highly toxic Group V precursors, arsine and phosphine. Tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP) are promising alternatives to AsH 3 and PH 3 . More recently, tris-dimethylaminoarsenic (DMAA) was explored as a possible As source for the growth of GaAs by OMVPE [1] and GaAs [2, 3] or GaAs/AIGaAs [4, 5] by MOMBE. Here, we examine the growth of AIGaAs, AIInP, and AlInAs by OMVPE using the alternative Group V precursors TBAs, TBP, and DMAA. Oxygen and carbon incorporation in Al-based III-V materials is of concern due to the high reactivity of Al. In a recent study, TBAs was shown to be more effective in suppressing intrinsic carbon incorporation (101 4 cm-3- 10 16 cm- 3 ) from trimethylgallium (TMGa) compared to AsH 3 [5]. We have reported that TBAs is also more effective than AsH 3 in suppressing extrinsic carbon incorporation using CC14 as the dopant [7, 8]. We have extended this comparison to the growth of AIGaAs with respect to both intrinsic and extrinsic carbon incorporation, and to oxygen incorporation. The surface morphology and oxygen concentration in AIInP using both PH 3 and TBP was also examined. The growth of AlGaAs and AllnAs using DMAA was explored. EXPERIMENTAL PROCEDURE The epitaxial layers were grown in a low-pressure (30 Torr) vertical-geometry OMVPE reactor described previously [8]. Hydrogen was used as the carrier gas. The precursors were the following: TMGa or triethylgallium (TEGa) for Ga; trimethylindium (TMIn) for In; trimethylaluminum (TMAI) for Al; AsH 3 , TBAs or DMAA for As; and TBP or PH 3 for P. Extrinsic carbon doping o
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