Zn O ∕ Mg 0.1 Zn 0.9 O multiquantum-well (MQW) structures were grown on ZnO substrates by molecular beam epitaxy. Abrupt interfaces and well/barrier width in the MQWs were confirmed by x-ray diffraction measurement and transmission electron microscopy. The transition energy of the localized exciton in the ZnO∕Mg0.1Zn0.9O MQWs with well/barrier width of 5∕8nm was found to be about 3.375eV at low temperature, consistent with theoretical calculation. The first subband energies in the conduction and valence band were calculated to be 19.2 and 5.4meV, respectively. The transition energy showed no shift with excitation power, indicating that the polarization-induced electric field is negligible in the ZnO∕Mg0.1Zn0.9O MQW structures.

We report on the formation of ohmic contacts to As-doped ZnO layers using a Pt/indium tin oxide ͑ITO͒ scheme. The As-doped ZnO layer shows p-type conductivity with carrier concentrations of 5.12-9.74ϫ10 16 cm −3 when annealed at 25-400°C for 1 min in nitrogen ambient. However, the ZnO layers exhibit n-type characteristics with carrier concentration ca.10 18 -ca.10 19 cm −3 when annealed at 500-800°C. The Pt/ITO contacts produce contact resistivities of 8.0ϫ10 −4 − 3.5ϫ10 −3 ⍀ cm 2 upon annealing at 300-600°C. Possible ohmic formation mechanisms for the Pt/ITO contacts to the As-doped ZnO layers are described and discussed.

We investigated the electrical properties of a GaN nanorod p-n junction diode patterned on a SiO2 substrate using e-beam lithography. The electron transport mechanisms were characterized by temperature-dependence and current-voltage measurements. At a low temperature, the current-voltage curves showed that the current slowly increased with a given voltage for the forward bias and hardly changed for the reverse bias, indicating the tunneling current dominates through the deep trap barrier. At a high temperature, however, the current-voltage curves exhibited strong temperature dependence suggesting that thermionic emission with an activation energy of 19.1meV over a barrier dominated.

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