In situ concentration monitoring in a vertical OMVPE reactor by fiber-optics-based Fourier transform infrared spectroscopy

We describe fiber-optics-based Fourier transform infrared (FOB-FTIR) spectroscopy for in situ monitoring of input partial pressures of organometallic precursors in a vertical rotating-disk organometallic vapor phase epitaxy reactor. Detection limits as low as 0.05 Torr for trimethylgallium and 0.006 Torr for tritertiarybutylaluminum (TTBAl) are achieved using a 1 s scan time, which are comparable to established ultrasonic measurements. In addition, the FOB-FTIR approach has the ability to detect parasitic Lewis acid-base interactions between organometallic precursors, as demonstrated for in situ measurements of TTBAl mixed with arsine, trimethylantimony or triethylantimony. Such observations are shown to provide insight into unexpected results in epitaxial growth.