Damage and Microstructure Evolution in GaN under Au Ion Irradiation
Damage and microstructure evolution in gallium nitride (GaN) under Au+ ion irradiation has been investigated using complementary electron microscopy, secondary ion mass spectrometry and ion beam analysis techniques. Epitaxially-grown GaN layers (2-um-thick) have been irradiated by 2.0 MeV Au ions to 1.0 × 1015 and 1.4 × 1015 cm-2 at 155 K and 7.3 × 1015 cm-2 at 200 K. The irradiation-induced damage has been analyzed by Rutherford backscattering spectroscopy in a channeling direction (RBS/C). For a better determination of ion-induced disorder profile, an iterative procedure and a Monte Carlo code (McChasy) are combined to analyze the ion channeling spectra. With increasing irradiation dose, separated amorphous layers develop from the sample surface and near the damage peak region. Formation of large nitrogen bubbles with sizes up to 70 nm is observed in the buried amorphous layer, while the surface layer contains small bubbles with diameter of a few nanometers due to significant nitrogen loss from the surface. Volume expansion from 3% to 25% in the irradiated region is suggested by cross sectional transmission electron microscope and RBS/C measurement. The anomalous shape of the Au distributions under three irradiations indicates out-diffusion of Au toward sample surface. The results from the complementary techniques suggest that nitrogen is retained in the damaged GaN where the crystallinity is preserved. Once the amorphous state is reached in the surface region, GaN starts to decompose and nitrogen escapes from the surface. Furthermore, experimental results show considerable errors in both disorder profile and ion range predicted by the Stopping and Range of Ions in Matter code, indicating a significant overestimation of electronic stopping powers of Au ions in GaN.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 974952
- Report Number(s):
- PNNL-SA-70396; 34899; KC0201020; KC0201020; TRN: US201007%%906
- Journal Information:
- Journal of Physics D. Applied Physics, 43(8):085303, Vol. 43, Issue 8
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
AMORPHOUS STATE
BUBBLES
CHANNELING
ELECTRON MICROSCOPES
ELECTRON MICROSCOPY
GALLIUM NITRIDES
ION BEAMS
ION CHANNELING
IRRADIATION
MASS SPECTROSCOPY
MICROSTRUCTURE
NITROGEN
RUTHERFORD BACKSCATTERING SPECTROSCOPY
SPECTRA
STOPPING POWER
damage profile
ion range
electronic stopping power
volume swelling
Environmental Molecular Sciences Laboratory