A mass spectrometric study of the simultaneous reaction mechanism of TMIn and PH3 to grow InP

The reaction mechanisms for the growth of InP from various mixtures of trimethyl indium (TMIn) and PH3 by OMVPE were investigated using mass spectrometry and a D2 ambient for isotopic labeling of the reaction products. It was found that, whereas TMIn alone pyrolyzes homogeneously, forming CH3D, and PH3 alone pyrolyzes heterogeneously, producing H2, the pyrolysis reactions of TMIn and PH3 together are completely different. The pyrolysis temperatures of both TMIn and PH3 are reduced (by 50 C for TMIn and 225 C for PH3), and the sole product is CH4 at high values of the PH3/TMIn ratio. The pyrolysis reaction is shown to be coupled (as evidenced by the equal depletion of TMIn and PH3 from the vapor) and, at temperatures below 400 C, heterogeneous.