A Qualitative Model for Predicting Alkyl Stability and its Relevance to Organometallic Growth of HgCdTe and GaAlAs

Abstract

ABSTRACTA qualitative stability model established for hydrocarbon molecules and extended to organometallic compounds is applied to alkyl organometallic compounds used in thin film growth. For hydrocarbon molecules the strength of a carbon-hydrogen bond is reduced by neighboring alkyl groups, The mechanism for this effect is delocalization of the unpaired electronic charge in the resultant free radical by neighboring alkyl groups. The delocalization effect is present in organometallic compounds and is illustrated here for several alkyl organometallic systems. Two applications of the delocalization effect in thin film growth are discussed. First the thermal stability of organotellurium compounds is substantially reduced in branched compounds which permits significantly lower HgCdTe metalorganic growth temperatures. Also carbon incorporation in GaAs and GaAlAs is reduced with ethyl instead of methyl organometallic compounds. An important factor contributing to this result is the weaker carbon-metal bonds in the ethyl compounds.