| ZnO is a direct wide bandgap semiconductor, the bandgap is about3.37eV at room temperature, and the exciton binding energy is60meV, far higher than room thermal ionization energy (26meV). Therefore, it can achieve high efficiency ultraviolet radiation luminescence at room temperature or higher temperature. This makes ZnO has important application in the preparation of ultraviolet light emitting diodes (LEDs) and laser devices (LDs). ZnO not only has some similar properties with GaN such as band gap, lattice constant and the thermal expansion coefficient, but also has some advantage which GaN doesn't have. As the third generation semiconductor materials ZnO shows great potential applications together with the GaN material.With in-depth study of ZnO material using in UV wavelength LEDs and LDs, people begin to pay attention to ZnMgO material. ZnMgO is formed by ZnO and MgO in a certain component. The same valence state of Mg atom and Zinc atom won't cause changes in carrier concentration, and the magnesium ions (Mg2+) radius (0.57A) is very close to the size of the zinc ions (Zn2+) radius (0.60A), which makes lattice mismatch caused by MgZn be very small, only0.1%. And the introduction of Mg makes the band gap of ZnO be continuously adjusted in the range of3.3-7.8eV. ZnMgO can also combine with ZnO to produce ZnO/ZnMgO superlattices, quantum wells and deep UV devices. But as the same as ZnO, the p-type doping problem of ZnMgO is also not well resolved, which makes exploring new method of preparing p-ZnMgO has very important scientific significance. In this thesis, we adopt metal organic chemical vapor deposition (MOCVD) technology, innovative use the sputtered GaAs interlayer as the acceptor doping source, successfully prepared p-ZnMgO:As films. And we also fabricate the p-ZnMgO/n-GaN light emitting devices. The specific work includes the following:(1) The preparation of high-quality ZnMgO films. The ZnMgO film was deposited on sapphire substrates by MOCVD technology. We detailed discussied the impact of growth temperature on film quality, and find the optimum growth temperature. To further improve the ZnMgO film quality, reduce the lattice mismatch and thermal mismatch between ZnMgO film and the substrate, ZnO buffer layer was introduced.By adjusting the growth temperature of buffer layer, we prepared high quality ZnMgO film finally.(2) The p-type doping of ZnMgO films. Through the analysis of several p-type doping mechanism, we chose the V group elements As as the dopant. Innovative introduced the sputtering GaAs interlayer to achieve As doping p-ZnMgO films. Through a set of variable temperature growth experiments, the propeties of ZnMgO:As were discussed in detail. The minimum resistivity p-ZnMgO film was26.33Ω·cm, with the carrier concentration was1.638x1017cm-3, mobility was1.45. X-ray diffraction (XRD) and photoluminescence (PL) test showed that the preparation of high temperature p-ZnMgO film had more good crystalline quality and optical quality.(3) The fabrication of n-GaN/p-ZnMgO heterojunction device and the study of its electroluminescence characteristics. First, the carrier concentration of5×1018cm-3n-GaN substrate was selected, and then p-ZnMgO:As film was prepared by sputtering GaAs interlayer, the order of carrier concentration was1017cm-3and then proceed to the fabrication of the device. The electroluminescence (EL) test showed that the heterojunction device had excellent electroluminescent properties, and the emitting area is mainly concentrated in the376nm in ultraviolet region, when the injection current reached150mA, the UV/visible ratio luminous intensity as high as35. |
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