MASS-SPECTROMETRIC STUDY OF THERMAL-DECOMPOSITION OF DIETHYLZINC AND DIETHYLTELLURIUM

A mass-spectrometric study of the thermal decomposition of Group II and VI alkyls involved in ZnTe growth by metal-organic chemical vapour deposition (MOCVD) is reported. The pyrolysis of diethylzinc (Et2Zn) and diethyltellurium (Et2Te) alone and together were followed with the change of the inlet partial pressure ratio (R = Te/Zn = 1 and 5). Under He and H-2, the thermal decomposition of Et2Zn organometallic species leads to the formation of n-C4H10, C2H4, and C2H6. The pyrolysis of Et2Te produces ethene in excess of other hydrocarbons. For co-decomposition in an He atmosphere, pyrolysis curves as a function of temperature, with R = 1 show that the temperature corresponding to the half-decomposition ratio (T50) of Et2Te is lowered by 25-degrees-C relative to that of Et2Te alone. For R = 5, the T50 of Et2Zn is increased by 30-degrees-C relative to that of the precursor alone. The kinetics of decomposition of Et2Zn and Et2Te alone showed no thermal hysteresis, whereas a strong hysteresis loop between heating and cooling of the susceptor was recorded during the co-decomposition. The dependence of these effects on R and temperature are discussed in relation to surface reactions.