COMPOSITION AND TEMPERATURE-DEPENDENCE OF THE OPTICAL-PROPERTIES OF ZN1-XCDXSE ESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.34) BELOW THEFUNDAMENTAL BANDGAP

The SI-VI ternary semiconductor alloy system Zn1-xCdxSe with 0 less th an or equal to x less than or equal to 0.2 has important applications as the active material in blue-green light-emitting diodes;and lasers, For the wavelength and temperature ranges over which these devices ar e designed to operate, a knowledge of the optical properties of the al lays is important. We report the results of spectroscopic ellipsometry measurements of the real part of the dielectric function epsilon(1) f or Zn-rich Zn1-xCdxSe layers deposited epitaxially on (100) GaAs. We d erive compact expressions that allow one to calculate accurate epsilon (1) spectra from 1.5 eV, the law-energy limit of our ellipsometer, to E-0 - 0.05 eV, where E-0 is the fundamental bandgap energy, for any co mposition and temperature within the ranges 0 less than or equal to x less than or equal to 0.34 and 25 less than or equal to T < 260 degree s C. Furthermore, we expect that the results can also be extrapolated to cover the substrate temperature range typically used for the growth of these films (250-300 degrees C). Hence the results presented here are also useful in future real-time spectroscopic ellipsometry studies of Zn1-xCdxSe film growth. (C) 1997 Optical Society of America.