Dislocation reduction in HgCdTe epilayers on GaAs by using CdTe/CdZnTe strained-layer superlattices in CdTe layers

The nucleation and growth of Hg1−xCdxTe on CdTe(211)B/Si(211) substrates by molecular beam epitaxy are comprehensively studied by in situ reflection high energy electron diffraction and transmission electron microscopy. Microtwins are observed to be formed at the interface, but are overgrown later as the growth proceeds. It is shown that the three-dimensional growth at the nucleation stage of HgCdTe on CdTe(211)B/Si and CdZnTe(211)B is more likely due to the higher surface energy of Hg1−xCdxTe than that of CdTe(211)B and CdZnTe(211)B.

Section: Resultsmentioning

confidence: 99%

Molecular beam epitaxial growth and structural properties of HgCdTe layers on CdTe(211)B/Si(211) substrates

Yang

Xin

Rujirawat

et al. 2000

“…In this experiment, the thickness of the HgCdTe layer was kept at a constant 6 m. Although the EPD of HgCdTe does not directly reveal the density of dislocations in CdTe, they have an almost linear relationship. 19 Therefore, the HgCdTe EPD can be employed as a relative indicator for the threading dislocation density of CdTe. We investigated the dependence of the HgCdTe EPD on the CdTe-layer thickness.…”

Section: Motion Of Threading Dislocationsmentioning

confidence: 99%

Misfit stress relaxation mechanism in CdTe(100) and CdTe/ZnTe(100) on a GaAs(100) highly mismatched heteroepitaxial layer

Sugiyama

Nishijima

1996

Self Cite

We studied the misfit stress in CdTe(100)/GaAs(100). In general, this highly mismatched system initially forms a ‘‘coincidence interface,’’ where seven CdTe lattices match with eight GaAs lattices. In this system, the epilayer is elastically strained by the mismatch remaining between both groups of lattices. Afterward, the misfit stress is gradually relaxed with the generation of misfit dislocations. In this work, we derived a new model to describe this misfit relaxation mechanism and verified it with experimental observations. As introducing the effects of the interface modification, we found that the simple force balance between the substrate and epilayer governed the misfit stress. We assume that the relaxation process during growth is similar to that in CdTe/CdZnTe, since the residual misfit was fairly small. By extending the stress relaxation model of CdTe/GaAs, it is possible to explain the strain in CdTe/ZnTe/GaAs, which contains two highly mismatched interfaces. The threading dislocations in HgCdTe, derived from the CdTe buffer, decreased with increasing CdTe thickness. Assuming that the misfit dislocations are generated by bending threading dislocations, we could explain the dislocation reduction by utilizing the above misfit stress relaxation model. In spite of the extremely large mismatch, the structural quality of CdTe(100)/GaAs(100) was improved due to the relatively small strain remaining in the coincidence interface.

“…7 Both screw and edge components of TDs exist in this epilayer as evidenced by various techniques. [7][8][9] However, in comparison with the edge TDs, the screw TDs are much more likely to have a higher density due to their lower dislocation energies according to a recent theoretical study. 10 This inevitably drives a need to study and to determine the density of screw TDs in the epilayers in much more detail and greater precision.…”

Section: Introductionmentioning

confidence: 99%

Identifying threading dislocations in CdTe films by reciprocal space mapping and defect decoration etching

Polat

Bilgilisoy

Arı

et al. 2018

We study threading dislocation (TD) density of high-quality cadmium telluride (CdTe) layers grown on a (211) oriented GaAs substrate by molecular beam epitaxy. High-resolution X-ray diffraction was performed to calculate the density of screw-type TDs by measuring the broadening of the asymmetrical (511) Bragg reflections of CdTe epilayers. In addition, total TD densities were determined by the Everson-etching method and were compared with screw TDs. Our results show that the total TD densities in CdTe films were dominated by those with screw character. The screw component TDs are estimated to account for more than 90% of the total TD density.CdTe layers grown at a thickness of less than 3.0 lm typically exhibit the screw TD densities in the 10 6 cm -2 and 10 7 cm -2 range. It can be noted that as the nucleation temperature increases, i.e., !222 C, both the area density of TDs with the screw component of the CdTe films and the total TD density are roughly four times larger than those of the epilayer grown at the nucleation temperature of 215 C. Furthermore, we discuss the influence of the II/VI flux ratio on the density of threading dislocations. The contribution of screw TDs to the total TD density showed a significant decrease in roughly 30% in the case of a high II/VI flux ratio. We further examine the reciprocal space maps in the vicinity of the (422) reflections.