APPLICATION OF PYROMETRIC INTERFEROMETRY TO THE IN-SITU MONITORING OFIN0.52AL0.48AS, IN0.53GA0.47AS, AND QUATERNARY ALLOY GROWTH ON INP SUBSTRATES

The alloy system In-0.525(AlxGa1-x)(0.475)As, which is lattice-matched to InP, covers the technologically important wavelength range 0.8-1.6 mu m, including the fiber optic communication wavelengths 1.3 and 1.5 5 mu m. However, growth of these alloys on InP is complicated by the s trong dependence of the lattice constant on In content, and would be i mproved by a convenient in situ method of growth monitoring. We consid er the feasibility of extending the method of pyrometric interferometr y (PI), whose utility is already established for AlxGa1-xAs/GaAs, to I n0.52Al0.48As, In0.53Ga0.47As, and general In-0.525(AlxGa1-x)(0.475)As growth on InP. We find that PI provides useful information about chan ges in the growth rate and-or composition. The method works best for h igh Al content films (e.g. In0.52Al0.48As) due to the larger band-gap, and requires about 0.8 mu m or thicker film growth for greatest accur acy. PI sensitivity is shown to be greater to changes in the In flux v ersus the Al flux. We determined the effective refractive index of In0 .52Al0.48As to be 3.515 for substrate temperature 500-550 degrees C. T he onset of In desorption as the substrate temperature is increased wa s also easily detected by PI.