Complex index of refraction of MBE grown 1 eV GaInAsNSb dilute nitride layers as a function of thermal annealing

Abstract

In this work, 1 eV GaInNAsSb layers with different thickness have been annealed to study the impact that the thermal treatments have on their optical properties. For such purpose, GaInNAsSb layers with thicknesses of 0.2, 1 and 3 μm were grown lattice-matched onto GaAs substrates. Each epiwafer was cut into four quarters: one quarter was left as the as-grown sample, another one was submitted to a Rapid Thermal Annealing, the third quarter was annealed in a Metal Organic Vapor Phase Epitaxy reactor, and the fourth one was submitted to the first annealing followed by the second one. The complex index of refraction of the samples has been determined using spectroscopic ellipsometry along a wide spectral range (250–2500 nm). The optical properties of the 1 and 3 μm as grown layers do not differ very much between them, while the 0.2 μm layer exhibits a particular behavior that can be correlated with similarities/differences in the dilute nitride layer composition. The two types of thermal annealing affect in a different way to both composition and optical properties of the GaInNAsSb layers depending on their thicknesses. Finally, the obtained refractive indices and extinction coefficients have been validated by simulating the experimental reflectance of the semiconductor structures. Therefore, the determination of the optical properties (ranging from 250 to 2500 nm) of 1 eV GaInNAsSb we present here, allows the simulation and optimization of optoelectronic devices incorporating this dilute nitride.