Measurement of the indium segregation in InGaN based LEDs with single atom sensitivity
In light emitting diodes (LED) consisting of GaN/InGaN/GaN quantum wells (QWs), the exact indium distribution inside the wells of the active region affects the performance of devices. Indium segregation can take place forming small InGaN clusters of locally varying composition. In the past, we used a local strain analysis from single HRTEM lattice images to determine the In composition inside the InGaN QWs with a resolution of 0.5 nm x 0.3 nm. Truly atomic resolution can be pursued by exploitation of intensity dependencies on the atomic number (Z) of the electron exit-wave (EW). In microscopes with sufficient sensitivity, local variations of amplitude and phase are found to be discrete with sample thickness, which allows for counting the number of atoms in each individual column of {approx}0.08 nm diameter. In QW s of {approx}17 percent of average indium concentration it is possible to discriminate between pure Ga columns and columns containing 1, 2, 3, or more In atoms because phase changes are discrete and element specific. The preparation of samples with atomically flat surfaces is a limiting factor for the application of the procedure.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science. Computational and Technology Research (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 816078
- Report Number(s):
- LBNL-53706; R&D Project: 518804; TRN: US0304893
- Resource Relation:
- Conference: SPIE International Symposium on Optical Science and Technology, San Diego, CA (US), 08/03/2003--08/08/2003; Other Information: PBD: 30 Jul 2003
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMPLITUDES
ATOMIC NUMBER
ATOMS
DISTRIBUTION
ELECTRONS
INDIUM
LIGHT EMITTING DIODES
MICROSCOPES
PERFORMANCE
RESOLUTION
SEGREGATION
SENSITIVITY
STRAINS
THICKNESS
INDIUM GALLIUM NITRIDE (INGAN) GALLIUM NITRIDE (GAN) QUANTUM WELL INDIUM (IN) DISTRIBUTION / SEGREGATION TRANSMISSION ELECTRON MICROSCOPY HRTEM PHASE CONTRAST EXIT WAVE RECONSTRUCTION (EWR)