Yuanda Liu

Cu related doublets green band emission in ZnO:Cu thin films

Cu-doped ZnO (ZnO:Cu) thin films were grown on Si (111) substrate by low-pressure metal-organic chemical vapor deposition equipment. The crystal structures and optical properties of as-grown sample were examined. X-ray diffraction patterns indicated a lattice relaxation after the Cu doping. The incorporation of Cu atoms into ZnO film and its existence in a bivalent state were demonstrated by x-ray photoelectron spectroscopy measurements. Low-temperature photoluminescence was carried out at temperature of 11.4 K for both unintentionally doped and Cu-doped ZnO films. A characteristic green-luminescence with fine structure consisted of doublets emission peak was observed, which was believed to be associated with Cu doping. A theoretical model based on hydrogen analog has been proposed to explain this phenomenon. It provides new information about the detailed role of Cu in ZnO thin films.

n-ZnO/p-GaN heterojunction light-emitting diodes with a polarization-induced graded-p-AlxGa1−xN electron-blocking layer

n-ZnO/p-GaN heterojunction light-emitting diodes (LEDs) with a polarization-induced graded-p-AlxGa1−xN electron-blocking layer (PIEBL) were fabricated. Compared with n-ZnO/p-GaN and n-ZnO/p-Al0.4Ga0.6N/p-GaN LEDs, the PIEBL can effectively block electron injection from ZnO to GaN and promote hole injection from GaN to ZnO. A dominant ZnO-related ultraviolet emission was observed from the edge emission of this device. The mechanism of PIEBL was also discussed in terms of polarization and energy band theory. This study suggests that PIEBL is an excellent electron-blocking layer for ZnO-based LEDs and laser diodes.

Dominant UV emission from p-MgZnO/n-GaN light emitting diodes

The authors report on the fabrication of p-Mg0.1Zn0.9O/n-GaN light emitting diodes (LEDs). Under forward bias, dominant ultraviolet (UV) electroluminescence is detected within 360-380 nm caused by near band edge (NBE) radiative recombination from both n-GaN and p-Mg0.1Zn0.9O. It is worth noting that the intensity ratio of UV-NBE/visible-DLE reaches up to 50, which indicates the potential applications of this structure in the short wavelength LEDs.