High Quality Single Crystalline Cubic MgZnO Films And Their Applications In Solar Blind Photodetection

The semiconductor optoelectronic devices worked in the deep ultraviolet region (200-300nm) have been paid much attention recently, due to their wide applications on the flame detection, missle flame detection and biochemical agents, et al. The cubic phased MgZnO films, as a wide band gap semiconductor, were considered the candidate as well as AlGaN materials. In 2008, the cubic MgZnO based photodetectors covered the whole solar blind region have been finished in our lab. As we known, in order to achieve deep ultraviolet photodetectors with high performance, the crystal and optical quality of the semiconductor films was necessary to be improved greatly. However, the phase separation always occurred up during the growth of the MgZnO films with high Mg or Zn contents, which was accepted as the main factor for the improvement of crystal quality of the MgZnO films.1. The cubic MgZnO films under different oxygen pressure (II/VI ratio) were grown on the sapphire substrate using the metal organic chemical vapor deposition (MOCVD) technique. It was found that the crystal quality and the surface morphology of the cubic phased MgZnO films have been greatly improved with the increase of the oxygen pressure.2. Single-crystalline MgZnO films were achieved in an oxygen-rich ambient at relatively low temperature. To explore the usefulness of the films in DUV optoelectronic devices, a solar-blind photodetector was fabricated from the MgZnO films, and the photodetector shows a responsivity of 396 mA/W at 10 V bias, more than three orders of magnitude larger than the largest value ever reported in MgZnO-based solar-blind photodetectors (0.1 mA/W). The dark current density of the photodetector is 1.5×10-11 A/cm2, comparable to the smallest value ever reported in DUV solar-blind photodetectors. The enhanced performance of the photodetector reveals that the single-crystalline cubic MgZnO films have great promising applications in DUV optoelectronic devices, and the results reported in this communication thus address a significant step towards such applications.3. High quality single crystalline MgZnO films with different Zn content were epitaxial grown on the MgO subtrate. The islands were found to be formed on the surface of the MgZnO films with high Zn content from SEM images. The mechanism was believed to be due to the stress existed between the MgZnO films and the MgO substrate.4. Photovoltaic solar blind detector was finished based on MgZnO/n-Si heterojunctions. The MgZnO/n-Si heterojunction based photodetectors showed solar blind property with peak responsivity of 1.2 mA/W at 280 nm at zero bias.