Model for the strain‐induced reflectance‐difference spectra of InGaAs/GaAs (001) epitaxial layers

Abstract

We present a model to describe the Reflectance-difference (RD) spectra of InGaAs grown on GaAs (001) at T=500 o C, in the energy range from 2.3-3.5 eV. The model assumes the presence of an orthorhombic strain in the InGaAs epilayer that accounts for an anisotropic process of nucleation of InGaAs islands. We show that the developed model leads to accurate fits to the experimental RD spectra of InGaAs/GaAs for epilayer thickness both below and above of the critical thickness for the 2D-3D growth-mode transition. From the fitting of the theoretical model to the experimental RD line shapes we obtain quantitative information on changes in surface stoichiometry and morphology at the onset of the 2D-3D transition. Our results demonstrate that the RD line shape of InGaAs/GaAs in the 2.3-3.5 eV energy range can be explained entirely in terms of surface-modified InGaAs E 1 and E 1 +∆ 1 bulk transitions with no need to invoke surface states.

In situ optical monitoring of the interface strain relaxation of InGaAs/GaAs grown by molecular‐beam epitaxy

“…We may thus conclude that the RD signal in the 3D growth comprise a substantial component originated in InGaAs islands that grow anisotropic. In agreement with this conclusion, elsewhere we have shown that the RD line shape of 3D In 0.3 Ga 0.7 As/GaAs (001) films in the energy range from 2.4-3.1 eV can be accurately modeled assuming that the InGaAs islands on the epilayer are under an orthorhombic strain [9,10]. This strain may be originated by the well-known anisotropy in the diffusion coefficients of the atomic species on the growth surface that may lead to InGaAs islands with anisotropic shapes [16] and thus with an anisotropic elastic strain relaxation.…”

“…Elsewhere, we reported on in situ RD measurements in In x Ga 1-x As grown by MBE that show a sharp increase in RD amplitude at 2.5 eV at the onset of the 2D-3D growth transition [9,10]. This, as a result of the formation of anisotropic 3D islands.…”

Reflection anisotropy spectroscopy

“…The insight that RAS has provided into the complexities of the GaAs(001) surface has naturally led to its use in the characterization of the early stages of the growth of semiconducting structures on GaAs(001). These range from the Si/GaAs(001) [50] and Ge/GaAs(001) systems [206][207][208], the latter prompted by the good lattice match between the materials, to systems where the lattice mismatch leads to the formation of quantum dots such as In/GaAs(001) [209][210][211][212]. RAS is also well suited to the study of the formation of metal-semiconductor contacts as illustrated by the studies of the interfaces between alkali metals and GaAs(001) [213,214] and of Cs deposited on a range of III-V (110) cleaved surfaces [215].…”

Reflectance‐anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs (001)

“…Such islands are fully strained at the base but partially relaxed at the top. Further, since it is known that such islands are anisotropic in shape [12,13], the strain at the top is also anisotropic. The same explanation can be adopted for RA oscillations during homoepitaxial growth.…”