MgZnO thin films were deposited on c-plane sapphire and fused quartz substrates with the same growth parameters by rf-reactive magnetron sputtering. Both the MgZnO thin films on the two substrates are single hexagonal phase and show similar Mg content. However, the absorption edge of MgZnO thin film on sapphire substrate shows a blue shift compared with that on fused quartz substrate. Similar shift also appears in the photoresponse of the detectors based on them. These phenomena were attributed to the more Mg atoms in grain boundary caused by the smaller grain size in MgZnO film on fused quartz substrate.

Cubic MgxZn1−xO thin films with Mg composition around 70% were deposited on A-plane and M-plane sapphire substrates by rf-reactive magnetron sputtering. Measured structural and optical properties of these thin films indicated an optimal annealing temperature of 700 °C which produced high quality cubic MgZnO thin films on both substrates. Moreover, when the annealing temperature exceeded 750 °C, a much rougher surface resulted, and several large mosaic particles on the surface of the annealed films appeared. From EDX results, the Mg composition was lower than that found in other sections of the annealed films. We attributed this to thermally induced reconstruction of the crystallites. This phenomenon was more obvious for annealed MgZnO films on A-plane sapphire than that on M-plane sapphire. Thermal expansion mismatch with the substrate is the principal reason.

The metal−semiconductor−metal ultraviolet (UV) photodetector was fabricated on the Mg0.47Zn0.53O layer grown by radio-frequency magnetron cosputtering. The photodetector shows the peak response at 290 nm with a cutoff wavelength at 312 nm. It exhibits a very low dark current of about 3 pA at 5 V bias, and the UV−visible rejection ratio (R = 290 nm/R = 400 nm) is more than 4 orders of magnitude. The transient response for the detector was measured, and it was found that the rise time is 10 ns and the fall time is 30 ns. The reason for the short response time is related to the Schottky structure.Keywords: Mg0.47Zn0.53O; MSM; RF magnetron cosputtering; UV photodetector

Wurtzite (Mg0.40Zn0.60O) thin films have been grown on quartz substrates by using the radio frequency magnetron sputtering technique, and a metal−semiconductor−metal Schottky barrier photodetector has been fabricated from these films. The photodetector exhibits a peak responsivity at 276 nm and a very sharp cutoff wavelength at 295 nm corresponding to the absorption edge of the Mg0.40Zn0.60O thin film. At 2 V bias, the detectivity of the photodetector is 1.1 × 1012 (cm Hz1/2)/W at 276 nm, and the ultraviolet-to-visible rejection ratio [R(276 nm)/R(400 nm)] is about 4 orders of magnitude. The photodetector also exhibits a very low dark current of about 100 pA at 2 V bias.

A Mg0.48Zn0.52O thin film was deposited on a sapphire substrate by metal-organic chemical vapor deposition, and the thin film exhibits a single cubic phase with high crystal quality from X-ray diffraction measurements. A metal–semiconductor–metal (MSM) structured photodetector was fabricated on the film. The device exhibits a peak response of 268 nm with a cutoff wavelength at 283 nm. Rise and decay times of 10 ns and 150 ns, respectively, are obtained with a load resistance of 50Ω. The pulse response for the device is limited by the RC time constant.

Diluted magnetic semiconductors Cd1−xFexSe were grown by metalorganic chemical vapor deposition. Their structure was studied by X-ray diffraction and selected area electron diffraction. The effect of Fe doping on the morphology and photoluminescence of CdSe was investigated. The photoluminescence study indicated that the crystalline structure of the Cd1−xFexSe films changed from a mixture of cubic and hexagonal phase to a single hexagonal phase with increasing Fe content.

In this paper, we have prepared Schottky type ZnO metal–semiconductor–metal (MSM) ultraviolet (UV) detector. The structural, electrical, and optical measurements were carried out. The detector exhibited a peak responsivity of 0.337 A/W at 360 nm and the dark current was about 1 nA under 3 V bias. An ultraviolet–visible rejection ratio was obtained about more than four orders of magnitude from the fabricated detector. The 10–90% rise and fall time were 20 ns and 250 ns, respectively. We proposed that the detector had shown a gain, which was attributed to the trapping of hole carriers at the semiconductor–metal interface.

Single-phase tetragonal FeSe films were grown on c-plane sapphire, SiO2, GaAs (100) and Si (100) substrates by low-pressure metal-organic chemical vapor deposition method. X-ray diffraction analysis shows that all the FeSe thin films on different substrates are of (00l) orientation. Spin-dependent magnet tunnel junction with Fe/ZnSe/FeSe structure were fabricated, and the tunneling magnetic resistance ratio decreased with increasing the thickness of ZnSe layer in the range of 10–20 nm.

A Mg0.48Zn0.52O thin film was deposited on a sapphire substrate by metal-organic chemical vapor deposition, and the thin film exhibits a single cubic phase with high crystal quality from X-ray diffraction measurements. A metal–semiconductor–metal (MSM) structured photodetector was fabricated on the film. The device exhibits a peak response of 268 nm with a cutoff wavelength at 283 nm. Rise and decay times of 10 ns and 150 ns, respectively, are obtained with a load resistance of 50Ω. The pulse response for the device is limited by the RC time constant.

Epitaxial growth of cubic Mg0.33Zn0.67O films on MgO (1 0 0) substrate by metalorganic chemical vapor deposition (MOCVD) was reported. X-ray diffraction (XRD) ω-scans and ϕ-scans demonstrate the films exhibit single (2 0 0) orientation and highly uniform in-plane orientation with four-fold symmetry. The epitaxial relationship between the layer and substrate is MgZnO (1 0 0)//MgO (1 0 0). Smooth surface with the rms roughness of 1.8 nm in 5×5 μm area is obtained. Atomic force microscopy (AFM) reveals formation of islands attributed to the strain in the epitaxial MgZnO films. These results demonstrate the high quality single crystal Mg0.33Zn0.67O films and their potential in high-performance deep ultraviolet optoelectronic devices.