p-ZnO Films Research Articles

Visual-infrared electroluminescence emission from ZnO∕GaAs heterojunctions grown by metal-organic chemical vapor deposition

The light-emitting diode of p-ZnO∕n-GaAs heterojunction was grown by metal-organic chemical vapor deposition. The p-ZnO films have been formed by the doping As atoms which diffuse into ZnO film from GaAs substrate. The p-type behavior of As-doped ZnO films based on As-doped p-ZnO∕n-GaAs, p-ZnO∕p-GaAs heterojunction was studied by carrying out I-V measurements and x-ray photoelectron spectroscopy. The I-V characteristic of p-ZnO∕n-GaAs heterojunction showed characteristic of rectifying diode and visual-infrared electroluminescence emission under forward current injection at room temperature. The I-V of the heterounction had a threshold voltage of ∼2.5V.

Origins of shallow level and hole mobility in codoped p-type ZnO thin films

A combination study of structural, optical, and electrical properties has been carried out on N–In codoped p-type ZnO thin films for the origins of shallow level and hole mobility. The observed small activation energy of ∼20meV for the hole concentration corresponds well to the results from photoluminescence and conductivity data, revealing the grain boundary trapping nature of the shallow level. The achieved hole mobility is mainly due to the lack of grain boundary barrier effect, and the codoping yielded weak ionized impurity scattering. The authors have also revealed the scattering and conduction mechanisms in these p-ZnO films.

Low resistivity p-ZnO films fabricated by sol-gel spin coating

N-doped and In-N-codoped ZnO films were fabricated on quartz glass substrate by sol-gel spin coating. Their p-type conductivities were characterized by the Hall measurements, revealing low resistivities of the order of 10−1Ωcm. Thin-film junctions comprising an undoped ZnO layer and a N-doped ZnO layer displayed the typical rectifying characteristics, suggesting formation of p-n homojunctions at the interfaces.

P -ZnO/n-GaN heterostructure ZnO light-emitting diodes

We report on the characteristics of a ZnO light-emitting diode (LED) comprised of a heterostructure of p-ZnO/n-GaN. The LED structure consisted of a phosphorus doped p-ZnO film with a hole concentration of 6.68×1017cm−3 and a Si-doped n-GaN film with an electron concentration of 1.1×1018cm−3. The I–V of the LED showed a threshold voltage of 5.4 V and an electroluminescence (EL) emission of 409 nm at room temperature. The EL emission peak at 409 nm was attributed to the band gap of p-ZnO which was reduced as the result of the band offset at the interface of p-ZnO and n-GaN.

Stable p-ZnO thin films by oxygen control using reverse spray dynamics

Semiconducting ZnO thin films were deposited on glass substrates by a modified CVD method using reverse spray of the precursor solutions. The films were characterized by X-ray diffraction (XRD) and Hall effect measurements at room temperature. The results of XRD analysis revealed polycrystalline nature of the grown films with different crystallographic orientations. The type of conductivity and the carrier concentration as determined from Hall effect measurements were dependent on the deposition temperature and annealing conditions. Oxygen control at 220 °C produced p-ZnO film with high hole mobility (193 cm 2/V s). The electrical conductivity was correlated to the stoichiometry of the grown films.

P-type in ZnO:N by codoping with Cr

ABSTRACTWe report on the fabrication of p-ZnO films by thermal oxidation of Zn3N2 deposited by reactive rf sputtering. With additional chromium doping we achieved p-type conductivity with the hole concentration ∼5×1017cm−3 and the mobility of 23.6 cm2/Vs at room temperature. We developed a method of surface passivation of p-ZnO that maintains its p-type conductivity over time-scale of months.