Study On MQWs And Alloy Of ZnO Films Made By Reactive Magnetron Sputtering

ZnO is aⅡ-Ⅵwide-band-gap (～3.3eV at room temperature) semiconductor with ahexagonal wurtzite structure. In terms of optoelectronics, its direct band gap and a largeexciton banding energy (60meV) should in principle lead to low thresholds for optical gaineven at room temperature. Due to the excellent physical and chemical properties, they can beintegrated with many semiconductor materials readily. ZnO films also have many realizedand potential applications such as surface acoustic wave devices, ultraviolet photodetectors,gas sensors, light emitters, transition layer for GaN and transparent conductors for display, etc.Now, a crucial step in designing ZnO-based optoelectronic devices is the realization ofband-gap engineering to create barrier layers and quantum wells in device heterostructures.This work is focus on the structural and optical properties of the ZnO-based materials, asfollow: ZnO/MgO quantum wells and ZnO-based films were grown on Si(100)(111) andquartz substrates with a RF reactive magnetron sputtering method. We use XRD, EPMA,transmission spectrum and photoluminescence analysis to test the microstructure, content andthe optical properties of the ZnO-based materials. This work is focus on the structural andoptical properties of the ZnO-based materials, as follow:ⅠWurtzite ZnO/MgO superlattices were successfully grown on Si (001) substrates at 750℃with a radio-frequency reactive magnetron sputtering method. X-ray reflection and diffraction,electronic probe and photoluminescence analysis were used to characterize the multiplequantum wells (MQWs). The results showed the periodic layer thickness of the MOWs to be1.85 to 22.3 nm. The blueshift induced by quantum confinement effect was observed. Afitting method based on the least square theory was used to deduce the zero phonon energy ofthe exciton from the room-temperature photoluminescence. It was found that MgO barrierlayers had a much larger offsets than ZnMgO. The fluctuation of periodic layer thickness ofthe MOWs was suggested to be a possible reason causing the photoluminescence broadening.ⅡZn_1-xMg_xO films (0=x=0.62) and Zn_1-xCd_xO films (0=x=0.10616) were grown on Si(111)and quartz substrates with RF reactive magnetron sputtering method. In the Zn_1-xMg_xO films,a strong c-axis orientation had been obtained at 750℃. We discussed the relationshipbetween crystal property and Mg incorporation. In addition, the Optical Band Gap of Zn_1-xMg_xO films is adjusted by Mg incorporation. The Optical Band Gap of the films had thesame pace with the increase of Mg incorporation. After annealing at 700℃, the orientation ofthe films had not been influenced so that annealing improved the crystal property ofZn_1-xMg_xO films. The defect photoluminescence was also weakened after annealing.Zn_1-xCd_xO films had a strong c-axis orientation with a Ti layer and ZnO layer deposited onthe substrate. The percentage of composition of Cd was between 0 and 10.616％. The FWHMof (002) diffraction peak of the wurtzite phase was in the same trend with the increace of Cdcontent. The films remained a hexagonal wurtzite structure within Cd incorporation x=10.616 with no obvious phase separation.