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Pseudomorphic ZnO‐based heterostructures: From polar through all semipolar to nonpolar orientations
Author(s) -
Grundmann Marius,
ZúñigaPérez Jesús
Publication year - 2016
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201552535
Subject(s) - wurtzite crystal structure , heterojunction , epitaxy , polar , materials science , condensed matter physics , piezoelectricity , polarization (electrochemistry) , isotropy , ferroelectricity , zinc , crystallography , optoelectronics , optics , chemistry , nanotechnology , physics , dielectric , composite material , metallurgy , layer (electronics) , astronomy
We calculate the strain and stress state and the polarization in pseudomorphic wurtzite Mgx Zn1 − x O/ZnO and Cdx Zn1 − x O/ZnO heterostructures as a function of the polar angle θ between the c ‐axis and the epitaxial direction. (Cd,Zn)O/ZnO behaves qualitatively similar to the systems (In,Ga)N/GaN and (Al,Ga)N/GaN. (Mg,Zn)O/ZnO represents a unique case since the signs of the change of lattice constants ∂ a / ∂ x and ∂ c / ∂ x are opposite. Among the consequences are: (i) the epilayer strain energy has a minimum between 0 ∘ and 90 ∘ for semipolar growth plane close to ( 11 2 ‾ 2 ) ; (ii) for nonpolar growth ( θ = 90 ∘ ) the strain in the epitaxial direction is close to zero; and the in‐plane polarization is large (comparable to the polar case); and (iii) the piezoelectric polarization along the growth direction has only one zero (at θ = 90 ∘ ) between 0∘ and 180 ∘ . Also we give useful analytical formula within an isotropic approximation for the compliances. Elastic strain energy (in relative units) of pseudomorphic wurtzite (Mg,Zn)O/ZnO and (Cd,Zn)O/ZnO heterostructures as a function of the polar angle θ between interface normal and the c ‐axis