RESUMEN
Temperature dependencies of the refractive indices, n, for InxGa1-xAs and InxAl1-xAs metamorphic layers with x=0.06-0.25 have been determined. For this purpose, we performed variable-temperature (80 to 400 K) measurements of the specular reflection coefficient using custom distributed-Bragg-reflector structures in the spectral range from 0.8 µm to 2.2 µm. All the compositions exhibited a nearly linear temperature dependence of n. For InxGa1-xAs, the temperature coefficient (dn/dT) increases from 2.0â 10-4K-1 for x=0.06 to 4.5â 10-4K-1 at x=0.25. In turn, the temperature coefficient of the InxAl1-xAs refractive index stays at the level of (1.7-2.0)â 10-4K-1 at the considered indium contents.
RESUMEN
Spectroscopic reflectometry was used within 700-1600 nm wavelength range to investigate dispersion curves for In0.06Al0.94As, In0.06Al0.1Ga0.84As, and In0.06Ga0.94As layers, which constituted the purpose-made metamorphic InAlGaAs/GaAs Bragg reflector (BR). The procedure for determining the refractive index based on analyzing variations in cross-correlation coefficient obtained for reflection coefficient calculated and experimental dependences is presented. The sensitivity of the proposed method for variations in refractive index was investigated depending on the number of BR periods, the extinction coefficient of the layers of BR, and the wavelength range with respect to the main reflection maximum.
RESUMEN
Hybrid quantum well-dots (QWD) nanostructures have been formed by deposition of 7-10 monolayers of In0.4Ga0.6As on a vicinal GaAs surface using metal-organic chemical vapor deposition. Transmission electron microscopy, photoluminescence and photocurrent analysis have shown that such structures represent quantum wells comprising three-dimensional (quantum dot-like) regions of two kinds. At least 20 QWD layers can be deposited defect-free providing high gain/absorption in the 0.9-1.1 spectral interval. Use of QWD media in a GaAs solar cell resulted in a photocurrent increment of 3.7 mA cm(-2) for the terrestrial spectrum and by 4.1 mA cm(-2) for the space spectrum. Diode lasers based on QWD emitting around 1.1 µm revealed high saturated gain and low transparency current density of about 15 cm(-1) and 37 A cm(-2) per layer, respectively.