Hydrogen in Wide Gap Semiconductor. Why many types of wide gap semiconductor have n type conductivity ? K.Shimomura (KEK-MSL). Impurity in Semiconductor. Shallow donor acceptor Bohr radious a= e ×(m e /m*)×a 0 ~20×a 0 Ionization Energy (13.6eV) × (m*/m e )/ e 2
Shallow donor acceptor
(13.6eV) × (m*/me)/ e2
Unintentional impurity difficult to study(less than ｐｐｍ).
Origin of n type conductivity in wide gap semiconductors.
More then 30 years old problem !
1.Direct Wide Band Gap Structure
Blue LED etc.
2.exhibit strong n type conductivity
Hydrogen behaves as a shallow donor/
Discovery of Weakly Bounded Muonium
S.F.Cox et. al Phys.Rev.Lett.86,1012(2001)
K.Shimomura et. al
1.Two kinds of Muonium have been clearly observed.
2.Both Muonium has axial symmetry along to  axis.
3.Hyperfine constants of the observed muoniums
are 10-4 times smaller than the muonium in va cuuum. These value is well correspond to the simple model calculation for shallow donor.
4.Ionization energy of these muoniums are also similar to the ionization energy of the un-intentional donor observed by Hall effect measurements.
These results indicate hydrogen could behave as a shallow donor and might be an origin of n type conductivity in ZnO.
Hydrogen negative U Deep center
J.Neugebaner, C.G.Van de Walle
C.G.Van de Walle, J.Neugebaner
Nature 423, 626(2003)
K.Shimomura et al PRL92,135505 (2003)
TRIUMF M15 12H ~600Mev.
A//=+337(10) kHz, A⊥=-243(30)kHz
Widely used as photo catalizer
Strong n type conductivity
Wide Ban Gap 3.3eV