Substrates for the Epitaxial Growth of MCT

First‐Principles Study of the 30° and 90° Partial Dislocations in HgTe, CdTe, and Hg0.7Cd0.3Te

“…Note that the high density of dislocation‐related states shown in Figure S2, Supporting Information is due to the high simulated dislocation areal density of ≈2.9 × 10 13 cm −2 for the 192‐atom supercell and ≈1.3 × 10 13 cm −2 for the 432‐atom supercell. This is in contrast to practical device‐grade materials that have much lower dislocation densities ranging from ≈10 4 cm −2 for higher quality materials to ≈10 6 cm −2 for lower quality materials, [ 5 ] and thus have a much lower density of dislocation‐related states within the energy bandgap. Nevertheless, these simulations allow us to observe the energy positions of the trap states that these dislocations introduce within the bandgap.…”

“…This may be a possible explanation for the enhanced interdiffusion of HgTe/CdTe superlattices in regions around dislocations. [ 5 ]…”

Molecular Dynamics Study of Heteroepitaxial Growth of HgCdTe on Perfect and Dislocated (211)B CdZnTe Substrates

“…While the lattice matching of CZT substrates reduces the formation of misfit dislocations, commercially available CZT substrates often have a high density of surface dislocations (∼10 4 cm −2 ), which thread into the MCT epilayer during MBE growth. 3 Threading dislocations are undesirable if they intersect the depletion region (the exact position in the epilayer depends on the specific device structure) of MCT detectors as they act as sources of tunnel current and 1/f noise, which limits the performance of these detectors. 4 Thus, a better understanding of how dislocations thread from the substrate to the epilayer during the growth process would assist in narrowing down the dominant types of dislocations that may be present in the MCT epilayer.…”

“…The production of high crystalline quality MCT is achieved by molecular beam epitaxy (MBE) growth on lattice-matched Cd 0.96 Zn 0.04 Te (CZT) substrates of a (211)B orientation. While the lattice matching of CZT substrates reduces the formation of misfit dislocations, commercially available CZT substrates often have a high density of surface dislocations (∼10 4 cm –2 ), which thread into the MCT epilayer during MBE growth . Threading dislocations are undesirable if they intersect the depletion region (the exact position in the epilayer depends on the specific device structure) of MCT detectors as they act as sources of tunnel current and 1/ f noise, which limits the performance of these detectors .…”

“…One of the benefits of such a study is the ability to investigate phenomena that would be impossible to observe experimentally, such as observing the first few nanometers of the growth process at the atomic scale. Furthermore, running MD simulations is cost- and time-efficient compared to MBE growth experiments if accelerated simulated growth rates are usedCZT substrates are costly (∼US $400 per wafer) and growth rates are slow (∼2–3 μm/h). Transmission electron microscopy (TEM) experiments for the analysis of the microstructure of MCT epilayers after growth are also challengingthinning samples to be transparent to electrons using argon ion milling can easily damage the material if proper milling conditions are not used …”