Strategies for Analyzing Noncommon‐Atom Heterovalent Interfaces: The Case of CdTe‐on‐InSb

Abstract

Semiconductor heterostructures are intrinsic to a wide range of modern‐day electronic devices, such as computers, light‐emitting devices, and photodetectors. Knowledge of chemical interfacial profiles in these structures is critical to the task of optimizing the device performance. This work presents an analysis of the composition profile and strain across the noncommon‐atom heterovalent CdTe/InSb interface, carried out using a combination of electron microscopy imaging techniques. Because of the close atomic numbers of the constituent elements, techniques such as high‐angle annular‐dark‐field and large‐angle bright‐field scanning transmission electron microscopy, as well as electron energy‐loss spectroscopy, give results from the interface region that are inherently difficult to interpret. By contrast, use of the 002 dark‐field imaging technique emphasizes the interface location by comparing differences in structure factors between the two materials. Comparisons of experimental and simulated CdTe‐on‐InSb profiles reveal that the interface is structurally abrupt to within about 1.5 nm (10–90% criterion), while geometric phase analysis based on aberration‐corrected electron microscopy images reveals a minimal level of interfacial strain. The present investigation opens new routes to the systematic investigation of heterovalent interfaces, formed by the combination of other valence‐mismatched material systems.

Electronic Structure and Epitaxy of CdTe Shells on InSb Nanowires

“…Moreover, their thermal expansion coefficients are comparable. [ 13 ] Besides their structural compatibility, CdTe has a large bandgap compared to InSb. Therefore, combining InSb with CdTe is compelling for several device applications such as, quantum‐well lasers, high electron mobility transistors, and infrared detectors.…”

Atomic-Resolution Structure Imaging of Misfit Dislocations at Heterovalent II–VI/III–V Interfaces

“…The lateral width of the curve, as measured from the 10 to 90% change of intensity, is then taken as a measure of the interface width. 34 Approximate interface widths for this ZnTe/GaSb heterostructure based on this criterion range from 0.72 to 1.08 nm. Thus, the interface is not chemically abrupt; i.e., there must be considerable chemical intermixing.…”

“…The profile peaks, which correspond to the positions of the atomic columns, have been fitted with a sigmoidal function, as shown by the pink lines on each profile. The lateral width of the curve, as measured from the 10 to 90% change of intensity, is then taken as a measure of the interface width . Approximate interface widths for this ZnTe/GaSb heterostructure based on this criterion range from 0.72 to 1.08 nm.…”

Moiré Fringe Method via Scanning Transmission Electron Microscopy

“…GPA is a widely used method to map the strain field from high resolution TEM images based on Fourier‐space‐based data processing, [ 25–31 ] and has been applied for various materials. [ 32–42 ] However, GPA method can be difficult to be directly applied to STEM images, as low‐sampled STEM images often lose detailed information at atomic scale, in addition to other artifacts such as scanning noise and scanning distortions etc. Alternatively, STEM‐MF offers a possibility of strain measurement from STEM images.…”