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Muonium as a shallow center in GaN
K Shimomura1, R Kadono, K Ohishi
1Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan.
Physical Review Letters
|April 20, 2004
Summary
Researchers discovered a paramagnetic muonium (Mu) state in gallium nitride (GaN) crystals. This finding suggests hydrogen may cause n-type conductivity in GaN.
Area of Science:
- Materials Science
- Solid State Physics
- Quantum Chemistry
Background:
- Muonium (Mu) is a light exotic atom, a hydrogenic system with a positive muon.
- Understanding muonium behavior provides insights into hydrogen in semiconductors.
- Gallium nitride (GaN) is a crucial semiconductor for electronic and optoelectronic devices.
Purpose of the Study:
- To investigate the properties and site of muonium in single-crystalline GaN.
- To explore the implications of muonium's behavior for hydrogen behavior in GaN.
- To determine if muonium can form shallow states in GaN.
Main Methods:
- Muon Spin Spectroscopy (µSR) was used to study paramagnetic muonium.
- Experiments were conducted on single-crystalline GaN below 25 K.
- Analysis focused on the hyperfine structure and ionization energy of muonium.
Main Results:
- A paramagnetic muonium state with a very small hyperfine parameter was observed in GaN.
- The muonium state exhibited highly anisotropic hyperfine structure with <0001> axial symmetry.
- The observed state has a small ionization energy (
Conclusions:
- Muonium likely occupies a nitrogen-antibonding or bond-centered site parallel to the c-axis in GaN.
- The shallow nature of the muonium state suggests analogous hydrogen centers could be responsible for n-type conductivity in as-grown GaN.