LIGAND-EXCHANGE REACTIONS IN INGAAS METALORGANIC VAPOR-PHASE EPITAXY

Metalorganic vapor-phase epitaxy of InyGa1-yAs from triethylgallium, t rimethylindium and tertiarybutylarsine was studied using on-line infra red spectroscopy to monitor the organometallic compounds in the feed a nd effluent gases. The film composition was measured by X-ray diffract ion. Ligand exchange reactions between the group III sources were foun d to occur in the feed lines. The new species produced were trimethylg allium, dimethylethylgallium, methyldiethylgallium, dimethylethylindiu m and methyldiethylindium. The thermal stability of these species vari ed over a wide temperature range. For example, the ethylindium compoun ds started to decompose at 250 degrees C, while trimethylgallium began to react at 500 degrees C. In the square-duct reactor used in this st udy, the wide variation in the reactivity of the precursors resulted i n films that were indium rich near the reactor inlet and gallium rich near the reactor outlet. (C) 1998 Elsevier Science B.V. All rights res erved.