High-resolution X-ray diffraction studies of molecular beam epitaxy-grown HgCdTe heterostructures and CdZnTe substrates

Abstract

Lattice mismatch between substrates and epitaxial layers of different molefractions can create a variety of distortions and defects in Hg (1-x) Cd (x) Te epilayers, thus degrading the performance of infrared detectors fabricated from this material. X-ray diffraction is a sensitive nondestructive technique, which allows in-depth characterization of the crystal lattice prior to detector fabrication. We present results of triple-axis diffractometry performed on single-and double-layer HgCdTe films grown on (211)B CdZnTe substrates by molecular beam epitaxy (MBE). In this study, both the ω and 2θ diffraction angles have been recorded absolutely so that the diffraction peaks in the RSMs can be positioned directly in reciprocal space, without requiring reference to a substrate peak. The positions of both surface-symmetric and asymmetric diffraction peaks have been used to extract lattice spacings parallel and perpendicular to the (211) growth direction. The relaxed lattice parameter of each epilayer has been calculated assuming that the layers are elastically strained. The low symmetry of the (211) growth direction, coupled with the anisotropic elasticity of zinc-blende semiconductors, results in monoclinic distortion of the lattice, as observed in these samples. In double-layer samples, the mosaicity of both layers is greater than that observed in single epilayers. Layers subjected to a Hg-saturated anneal show greater lattice distortion than as-grown samples.

Strain states and relaxation for $$\alpha$$-(Al$$_x$$Ga$$_{1-x}$$)$$_2$$O$$_3$$ thin films on prismatic planes of $$\alpha$$-Al$$_2$$O$$_3$$ in the full composition range: Fundamental difference of a- and m-epitaxial planes in the manifestation of shear strain and lattice tilt

“…[45]. The shear strain results in a rotation of the asymmetric reflections in reciprocal space by s around the symmetric (30.0) reflection [51][52][53] as indicated in Fig. 1a.…”

Structure and Interface Analysis of Diamond on an AlGaN/GaN HEMT Utilizing an in Situ SiNx Interlayer Grown by MOCVD

“…By determining the exact x value for the strained barrier layer, ε xx and ε zz were determined and are presented in Table . Strain in III-nitride layers may be composed of hydrostatic (ε h ) and biaxial (ε ii b ) components, ,, where i represents direction x or z . As a result of the significantly different covalent radii of the Ga and the N atoms, GaN is prone to native defect formation .…”

Investigation of HgTe-HgCdTe superlattices by high-resolution X-ray diffraction

“…Based on Vegard's law and the lattice constants of CdTe and ZnTe, 17 the variation measured in these two substrates corresponds to change in zinc content of 3.3-3.5% for the (112) orientation, and 3.1-3.5% for the (001) orientation, a similar variation seen by other researchers. 10,19 This variation has been attributed to zinc segregation during the bulk growth of the boules from which the substrates are cut. 20 Both the (001) and (112) superlattices show comparable FWHM values in 2u over the surface of the wafer, as seen in Figs.…”

“…Reciprocal space mapping can be performed, which can resolve both variations in lattice spacing and lattice tilt associated with the substrate and grown layer, as well as lattice spacings both parallel and perpendicular to the growth direction. The latter spacing is used to characterize the strain state of the grown layers, which has previously been performed on (112) HgCdTe single layers, 9 heterostructures, 10 and superlattices. 11 Reported here is the study of a number of molecular beam epitaxy (MBE) grown (001) and (112) HgTe-HgCdTe superlattices using this technique.…”