Thick Epitaxy of AlN and AlGaN with controlling source molecules and nano-crystal field.

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Since AlN and AlGaN have lattice constants close to that of GaN, high thermal conductivity and wide band gap, AlN and AlGaN have been identified as a promising substrate material for the fabrication of high-power electronic devices and ultraviolet(UV) optoelectronic devices. A promising growth system is a Hydride Vapor Phase Epitaxy(HVPE), which delivers a high growth rate. However, investigations concerning HVPE of AlN have been limited, because AlCl used as a source molecule of Al reacts with quarts(SiO_2).By the thermodynamic analysis and the experiment in the investigation, it was found that AlCl_3 doesn't react with SiO_2 and HVPE of AlN is possible using AlCl_3 and NH_3 as source gases. Then, we tried to grow AlN layer by HVPE system. Successful AlN HVPE on sapphire substrates was shown. Aθ-2θ mode X-ray diffraction(XRD) profile of the layer (2.1μm thickness) grown with input partial pressures of HCl and NH_3 of 6.0 x 10^<-3> atm and 4.0x10^<-2> atm, respectively. In addition, aside from the peaks due to the sapphire substrate, only the diffraction peaks related to c-axis-oriented hexagonal AlN was onserbed.Next, we investigated a thermodynamic analysis a possibility of HVPE growth of AlGaN ternary alloys. In HVPE system for AlGaN alloy, the source molecules are AlCl_3,GaCl and NH_3. A thermodynamic analysis of HVP) of AlGaN using AiCl_3 and GaCl as group III precursors is described. For a range of values on the input ratio, temperature, and the partial pressure of hydrogen in the carrier gas, we calculated the equilibrium partial pressures and the driving force for AlN and GaN deposition in AlGaN. As a result, we showed that controllable AlGaN HVPE is possible under a low partial pressure of hydrogen (<10% hydrogen in carrier gas).