Direct observations of defect structures in optoelectronic materials by Z-contrast STEM

Conference · Sun Feb 01 04:00:00 EST 1998

OSTI ID:650186

Xin, Y ^[1]; Browning, N D ^[1]; Pennycook, S J ^[2]

---

1. Univ. of Illinois, Chicago, IL (United States). Dept. of Physics
2. Oak Ridge National Lab., TN (United States). Solid State Div.; and others

Optoelectronic semiconductor materials have wide and important technological applications. For example, wide gap nitride semiconductors have attracted significant attention recently due to their promising performance as short-wavelength light emitting diodes (LEDs) and blue lasers, while HgCdTe II-VI semiconductors are the most promising candidates for applications as infrared detectors, or large array x-ray or gamma-ray detectors. In this paper, two examples are given to show that high-resolution Z-contrast imaging is an effective technique to determine the atomic structures of defects in these complex semiconductor materials. One interesting issue concerning GaN is that the material is relatively insensitive to the presence of a density of dislocations which is six orders of magnitude higher than that for III-V arsenide and phosphide based LEDs. To develop a fundamental understanding of the properties of the dislocations in GaN, the core structures are determined here by atomic-resolution Z-contrast imaging in a scanning transmission electron microscope (STEM) with a resolution of 0.13 nm. As the Z-contrast image is a convolution between the probe intensity profile and the specimen object function, it is possible to obtain detailed information on the atomic column positions through maximum entropy analysis. For a sphalerite semiconductor, polarity is an important issue, as the asymmetry of the structure gives rise to different physical and chemical properties. Here the authors show that high resolution Z-contrast imaging could be used as an effective method to determine the polarity of II-VI semiconductors without referring to reference samples or image simulations.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 650186
• Report Number(s): ORNL/CP--97026; CONF-980713--; ON: DE98004963; BR: KC0202040
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CADMIUM TELLURIDES
DEFECTS
ELECTRONIC STRUCTURE
GALLIUM NITRIDES
MERCURY TELLURIDES
SCANNING ELECTRON MICROSCOPY
SEMICONDUCTOR MATERIALS
TRANSMISSION ELECTRON MICROSCOPY