517 research outputs found
Hole Transport in p-Type ZnO
A two-band model involving the A- and B-valence bands was adopted to analyze
the temperature dependent Hall effect measured on N-doped \textit{p}-type ZnO.
The hole transport characteristics (mobilities, and effective Hall factor) are
calculated using the ``relaxation time approximation'' as a function of
temperature. It is shown that the lattice scattering by the acoustic
deformation potential is dominant. In the calculation of the scattering rate
for ionized impurity mechanism, the activation energy of 100 or 170 meV is used
at different compensation ratios between donor and acceptor concentrations. The
theoretical Hall mobility at acceptor concentration of
cm is about 70 cmVs with the activation energy of 100 meV
and the compensation ratio of 0.8 at 300 K. We also found that the compensation
ratios conspicuously affected the Hall mobilities.Comment: 5page, 5 figures, accepted for publication in Jpn. J. Appl. Phy
Polarization dependent Landau level crossing in a two-dimensional electron system in MgZnO/ZnO-heterostructure
We report electrical transport measurements in a tilted magnetic field on a
high-mobility two-dimensional electron system confined at the MgZnO/ZnO
heterointerface. The observation of multiple crossing events of spin-resolved
Landau levels (LLs) enables the mapping of the sequence of electronic states.
We further measure the renormalization of electron spin susceptibility at zero
field and the susceptibility dependence on the electron spin polarization. The
latter manifests the deviation from the Pauli spin susceptibility. As the
result, the crossing of spin-resolved LLs shifts to smaller tilt angles and the
first Landau level coincidence event is absent even when the magnetic field has
only a perpendicular component to the 2DES plane.Comment: 5 pages, 4 figure
Gallium concentration dependence of room-temperature near-bandedge luminescence in n-type ZnO:Ga
We investigated the optical properties of epitaxial \textit{n}-type ZnO films
grown on lattice-matched ScAlMgO substrates. As the Ga doping concentration
increased up to cm, the absorption edge showed a
systematic blueshift, consistent with the Burstein-Moss effect. A bright
near-bandedge photoluminescence (PL) could be observed even at room
temperature, the intensity of which increased monotonically as the doping
concentration was increased except for the highest doping level. It indicates
that nonradiative transitions dominate at a low doping density. Both a Stokes
shift and broadening in the PL band are monotonically increasing functions of
donor concentration, which was explained in terms of potential fluctuations
caused by the random distribution of donor impurities.Comment: accepted for publication for Applied Physics Letters 4 figure
Nonlinear response of a MgZnO/ZnO heterostructure close to zero bias
We report on magnetotransport properties of a MgZnO/ZnO heterostructure
subjected to weak direct currents. We find that in the regime of overlapping
Landau levels, the differential resistivity acquires a quantum correction
proportional to both the square of the current and the Dingle factor. The
analysis shows that the correction to the differential resistivity is dominated
by a current-induced modification of the electron distribution function and
allows us to access both quantum and inelastic scattering rates.Comment: 4 pages, 3 figure
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