Tianpeng Yang

Preparation of intrinsic and N-doped p-type ZnO thin films by metalorganic vapor phase epitaxy

The intrinsic p-type ZnO thin films were prepared by controlling the oxygen partial pressure during growth. The E2 (high) mode at 432.2cm−1 appeared in the Raman spectrum of the film. The photoluminescence spectra taken at 77 K showed the emission band C in the violet region, which originated from zinc vacancy and varied in intensity in accordance with the quantity of the carrier concentration in the films. The N-doped p-type ZnO films were realized by N2 plasma. The Raman spectrum showed the dominant A1 (LO) mode at 580cm−1, that was the result of the host-lattice defects generated by N dopant rather than the N-related local vibration modes.

Room temperature defect related electroluminescence from ZnO homojunctions grown by ultrasonic spray pyrolysis

ZnO homojunction light-emitting diode was grown on single-crystal GaAs (100) substrate by ultrasonic spray pyrolysis. This diode was comprised of N–In codoped p-type ZnO and unintentionally doped n-type ZnO film. Ohmic contact on n-type ZnO layer and GaAs substrate was formed by Zn∕Au and Au∕Ge∕Ni alloyed metal electrodes, respectively. An electroluminescence emission associated with defects was observed from the ZnO homojunction under forward current injection at room temperature. The I-V characteristics of the homojunction showed a threshold voltage of ∼4V under forward bias.

Effect of annealing on ZnO thin films grown on (001) silicon substrate by low-pressure metalorganic chemical vapour deposition

ZnO thin films were deposited on (001) Si substrate by low-pressure metalorganic chemical vapour deposition. Thermal annealing was performed at 800 °C in air for an hour. The effects of annealing on the surface morphology, stoichiometric ratio, structural and optical properties of ZnO films were investigated using scanning electron microscopy, x-ray photoemission spectroscopy (XPS), x-ray diffraction, Raman spectra and photoluminescence spectra. The resistivity of ZnO film increased to 1.25 × 102 Ω cm after annealing. It was found that the quality of ZnO film could be improved through annealing.

Structural and optoelectrical properties of ZnO thin films deposited on GaAs substrate by metal-organic chemical vapour deposition (MOCVD)

ZnO thin films were deposited on semi-insulating (0 0 1) GaAs substrates at different growth conditions by metal-organic chemical vapour deposition. The effect of growth temperature and ambient oxygen partial pressure on the properties of the ZnO films was studied. It was found that these two important parameters affected the structure, crystallinity, surface morphology, and optical and electrical characteristics of the ZnO films. At the present growth conditions, the full width at half maximum of a ZnO (0 0 2) diffraction peak decreased to 0.185° at 610 °C under an oxygen partial pressure of 45 Pa. By increasing the oxygen partial pressure from 45 to 68 Pa, the surface of the ZnO films became smoother and the grain size smaller and more homogeneous. In addition, the near-band-edge emission and the deep-level emission in the photoluminescence spectra and the electrical properties of the ZnO thin films strongly depended on the ambient oxygen content.

Green electroluminescence from ZnO/n-InP heterostructure fabricated by metalorganic chemical vapour deposition

Vertically aligned ZnO films were deposited on n-InP by metalorganic chemical vapour deposition. X-ray diffraction, field emission scanning electron microscopy and photoluminescence measurements demonstrated that the ZnO films had good quality. By evaporating AuZn electrodes on both ZnO and InP surfaces, a ZnO-based light emitting device was fabricated. Under forward voltage, weak green emissions can be observed in darkness.

Optical and electronic properties of ZnO:P/n+-Si heterostructures fabricated by metalorganic chemical vapour deposition

ZnO:P/n+-Si heterostructures were fabricated on n+-Si substrates by metalorganic chemical vapour deposition. The substrates were heavily doped with phosphorus. The crystallinity and optical properties of ZnO films were characterized by photoluminescence spectra and x-ray diffraction, respectively. X-ray photoelectron spectroscopy (XPS) showed that phosphorus atoms existed in ZnO films. The current–voltage (I–V) curve showed current rectification characteristic behaviour.