DECOMPOSITION OF CYANOETHYLPHOSPHINE, BENZYLPHOSPHINE, AND CYCLOPENTYLPHOSPHINE DURING INP MOCVD GROWTH STUDIED BY FTIR SPECTROSCOPY - CRITERIA FOR THE DESIGN OF ORGANOPHOSPHINE PRECURSORS

Ex situ Fourier transform infrared spectroscopic data are presented fo r the decomposition of cyanoethylphosphine (CYEP), benzylphosphine (BZ P), cyclopentylphosphine (CPP), and mixtures of these phosphines with trimethylindium (TMIn) under atmospheric pressure metallorganic chemic al vapor deposition (MOCVD) conditions using dihydrogen carrier gas. I R bands due to CYEP, BZP, CPP, TMIn, and their decomposition products have been monitored as a function of susceptor temperature. The decomp osition of CYEP, BZP, and CPP alone in dihydrogen commenced at tempera tures >723, 723, and 823 K, respectively, while in the presence of TMI n the onset of decomposition occurred at the lower temperatures of 623 , 523, and 573 K, respectively In afl cases the decomposition was acco mpanied by the formation of phosphine and related hydrocarbons which m ay be attributed to the operation of either beta-elimination or free-r adical reaction mechanisms. In the presence of TMIn a room temperature prereaction was observed for all precursors, the only detectable prod ucts of which were methane and involatile solids or liquids. By compar ison with previous data obtained for cyclohexylphosphine and tertiaryb utylphosphine it is suggested that the involatile solids formed in the presence of TMIn are polymers of the type [MeIn-PR]n and we propose t hat the extent of organophosphine prereaction with TMIn is governed by a combination of steric factors influencing the extent of polymerizat ion and the stability of the species resulting from cleavage of the P- C bond.