Growth And Doping Of Al_xGa_1-xN Based Materials For Ultra-violet Opto-electronic Devices

Al_xGa_1-xN is direct bandage materials with broad bandwidth, stable chemical property,thermo-stability and anti-radiation. It’s wavelength can change continually from200nm to365nm, making it potential in chemical detecting, biological weapons warning of biologicalagents, water and air purification, sterilization and disinfection, semiconductor solid-statelighting and so on.This thesis optimized the growth of AlN template, high Al-composition AlGaNmaterials, n-type doping and p-type GaN doping aiming at the problems that exists inAl_xGa_1-xN based opto-electronic devices by MOCVD. The crystal quality、 surfacemorphology and electrical properties of the epitaxial material were analysed using X-raydouble crystal diffraction analyzer （XRD）, atomic force microscopy （AFM）, transmissionspectrum test, Hall testing and so on. The experiments were listed as follows：1. High-quality AlN template was grown using the two-step growth method （lowtemperature nucleation layer+high pulse atom epitaxial layer）, and how temperature ofLT-nucleation layer and the Ⅴ/Ⅲ of HT-PALE layer influence the quality of AlN templatewas studied. The results indicate that if the temperature rise up appropriately, the lowtemperature nucleation sites will become large, which is conducive to the growth of hightemperature PALE AlN layer; as Ⅴ/Ⅲ of HT-PALE layer decreases, the migration distanceof Al will increases, which can benefit the healing of the three-dimensional island nucleationpoint, then form two-dimensional growth, finally improves the surface morphology.2. High Al composition n-AlGaN materials was grown on AlN template usingsuper-lattice technology to study how SiH4/（TMA+TEG）influence the quality of n-AlGaNmaterials. The results show that, within a certain range, enlarging the SiH4（TMA+TEG）isconducive to reducing the point defects, and alleviate the stress, thereby reducing the edgedislocation density and the resistivity reduction, increasing the carrier concentration. Inaddition, when the Al component increases，the conductivity of the sample decreases due to activation of Si getting larger.3. p-GaN materials were grown on AlN template, and the way the annealingtemperature affecting the p-GaN material quality was studied. The results show that, as theannealing temperature increases, the crystal quality is better. A possible reasonis that annealing promote the release of stress and recrystallization,which makes defectsdecreases and the dislocation density decreased, and finally improve the crystalquality.Studies have shown that, when the annealing temperature of800°C, the bestelectrical properties.