Optical properties of tensile-strained and relaxed Ge films grown on InGaAs buffer

Abstract

GeO 2 /Ge/In x Ga 1Àx As heterostructures grown on (100) GaAs substrates were studied using Raman spectroscopy and photoluminescence (PL) spectroscopy. Both nearly pseudomorphic tensile-strained and nearly completely relaxed Ge films were grown and studied. The maximum tensile strain for Ge films with a thickness of %7 nm reaches 2.25%. PL data confirm the conclusions that the band gap offset of Ge/In x Ga 1Àx As is sensitive to the polarity of the bonds at the interface, and also to a parameter of x and the relaxation of strain. Depending on these parameters, the Ge/In x Ga 1Àx As may be type-I or type-II heterostructures. V

First-Principles Calculations of Band Offsets at Heterovalent ε - Ge/InxAl1−xAsGreene‐Diniz1, Grüning2 2018Phys. Rev. Applied3100View full textAdd to dashboardCite

“…Band offsets (BOs) across pseudomorphic heterostructures exhibiting heterovalent bonding across the interface have also been studied, both experimentally 7,[21][22][23][24][25] and computationally. 7,10,23,[26][27][28][29] As for the isovalent interfaces, a large portion of the computational (atomistic modeling) studies also involve ideal, abrupt interfaces, although some focus has been given to atomic intermixing/diffusion across the interface.…”

Redshift of the absorption edge in tensile-strained germanium layers

“…It is known that mechanical strain and nanostructuring change the energy band structure of semiconductor materials [1][2][3][4][5]. Thus, the authors of [6] reported that their photoconductivity measurements provide exper imental evidence of a reduction of the band gap in ten sile strained silicon to 0.59 eV.…”

“…The LO phonon mode is singlet, and the shift of its frequency as a function of the strain tensor is well investigated. If ε xx = ε yy and the ε zz component of the strain tensor is determined by the Poisson coef ficient, ΔΩ(Ge LO ) = -4.2ε xx , where the strains are in percent [5,9]. Then, we can easily find that the tensile strain is 1.9 and 1.5% in the samples with five and ten Ge layers, respectively.…”

“…For this band alignment, the energy of these transitions is lower than the band gap of Ge. For more accurate analysis, one needs either to control the polarity of the bonds at the interface during growth or to use a buffer with a wider gap, such as InAlAs alloy [5,13].…”

“…Tensile strain in Ge films in the growth plane can be as large as 2.33% [4,5,8]. Changes in the optical properties of Ge in such struc tures were studied using photoluminescence spectros copy.…”