The Indices of Refraction of Molecular-Beam Epitaxy-Grown Be_xZn_(1-x)Te Ternary Alloys

摘要

We have used a combination of prism-coupling, reflectivity, and ellipsometric techniques to investigate the indices of refraction, n, of a series of Be_xZn_(1-x)Te thin films grown on InP substrates. After determining the concentrations of each of the Be_xZn_(1-x)Te alloys using x-ray diffraction measurements, we measured their n at discrete wavelengths using a prism-coupler setup. In addition, we used reflectivity measurements to complement the prism-coupler data and arrive at the dispersion relations of n for the Be_xZn_(1-x)Te alloys below their fundamental energy gaps. We then employed a rotating analyzer-spectroscopic ellipsometer to measure the complex reflection ratio for each of the films at angles of incidence of 65 deg, 70 deg, and 75 deg. By using the n values obtained from both the prism-coupler and the reflection-spectroscopy technique to guide the ellipsometric analysis, we were able to obtain accurate results for the dispersion of a for the Be_xZn_(1-x)Te alloys, not only below their fundamental energy gaps, but also above their energy gaps (up to 6.5 eV) using these three complementary techniques.