In situ measurement of the thermal and photo-assisted MOVPE of ZnTe using laser reflectometry

In situ laser reflectometry has been used to study the growth kinetics of ZnTe under pyrolytic and photo-assisted conditions from diisopropyltellurium (DIPTe) and dimethylzinc.triethylamine (DMZn.TEN). The growth rate of ZnTe was monitored as a function of VI:II ratio, temperature and laser power density. From the results a model for the growth involving the surface decomposition of DIPTe via a bimolecular reaction with methyl radicals homolytically released from the decomposition of DMZn.TEN is proposed. The activation energy under pyrolytic conditions in the low temperature regime for a 1:1 VI:II ratio was found to be 27.6 kcal/mol and under photo-assisted conditions this activation energy was seen to be lowered to 21.9 kcal/mol. The growth kinetics are explained in terms of two competitive processes. The decomposition of DMZn on the surface will be enhanced with increasing substrate temperature; however, the desorption rate of DIPTe will also be enhanced. The competitive nature of these two processes is seen to be particularly pronounced under laser illumination at high power densities, where a growth rate of 13 a.u./s was observed at 360 degrees C, laser power density 67 mW/cm(2), whereas at 380 degrees C for a similar power density the growth rate was seen to be reduced to 10.5 a.u./s.