Insight into precursor kinetics using an infrared gas analyser

Precursor kinetics and its influence on MOCVD growth was investigated using an infrared absorption gas analyser. After several refinements, the analyser was able to be used to measure time dependent concentrations of precursors in the growth zone. Changes were induced by periodic switching of corresponding bubbler valves. It was proved that precursor transport could be accurately described by the combined plug flow and perfectly mixed tank model. The studies of the precursor trans-port are strategically important for the growth of multilayer structures, when growth time of particular layers becomes comparable to delays and time constants. One example is quantum wells or interdiffused multilayer process (IMP) used in the growth of Hg1-xCdxTe heterostructures, where knowledge of precursor transport characteristics is vital for understanding and properly designing that growth. The model parameters, sc. the delays and time constants for DIPTe and DMCd, were evaluated for various growth conditions and then successfully used to optimise the growth of complex Hg_1−xCd_xTe heterostructures.