21 June 2004 Reflectivity fitting for accurate thickness and compositional determination in RCLEDs
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Abstract
Using a least squares technique we fit the measured normal-incidence reflectivity spectra of resonant cavity light emitting diode (RCLED) structures, using six fitting parameters-the thicknesses of the AlAs and AlGaAs layers in the top and bottom Bragg stacks, the thicknesses of the cavity region, and the Al concentration in the AlGaAs components of both Bragg stacks. We find that the fitting procedure indicates growth errors in these thicknesses and in the Al concentrations, and, in particular, gives a best fit when the Al concentration in the AlGaAs component of the Bragg mirrors is typically 61±1% instead of the intended 50%. Furthermore, the fitting reveals that the spatial period of the upper Bragg stack is typically 4% less than that in the lower stack, in these growth runs, a finding which is confirmed by a detailed analysis of scanning electron microscopy images of cleaved pieces of the RCLED wafers. This fitting method provides a useful and non-destructive tool to determine as-grown thicknesses and compositions of complex multilayer heterostructures which are otherwise difficult to ascertain.
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Terry E. Sale, Terry E. Sale, Konstanze Hild, Konstanze Hild, T. J.C. Hosea, T. J.C. Hosea, Masumi Hirotani, Masumi Hirotani, Y. Kato, Y. Kato, } "Reflectivity fitting for accurate thickness and compositional determination in RCLEDs", Proc. SPIE 5366, Light-Emitting Diodes: Research, Manufacturing, and Applications VIII, (21 June 2004); doi: 10.1117/12.529654; https://doi.org/10.1117/12.529654
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