Ligand exchange reactions in InGaAs metalorganic vapor-phase epitaxy

Metalorganic vapor-phase epitaxy of InyGa1-yAs from triethylgallium, trimethylindium and tertiarybutylarsine was studied using on-line infrared spectroscopy to monitor the organometallic compounds in the feed and effluent gases. The film composition was measured by X-ray diffraction. Ligand exchange reactions between the group III sources were found to occur in the feed lines. The new species produced were trimethylgallium, dimethylethylgallium, methyldiethylgallium, dimethylethylindium and methyldiethylindium. The thermal stability of these species varied over a wide temperature range. For example, the ethylindium compounds started to decompose at 250 degrees C, while trimethylgallium began to react at 500 degrees C. In the square-duct reactor used in this study, the wide variation in the reactivity of the precursors resulted in films that were indium rich near the reactor inlet and gallium rich near the reactor outlet. (C) 1998 Elsevier Science B.V. All rights reserved.