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

由于AlN和AlGaN具有接近GaN的晶格常数，高导热性和宽带隙，AlN和AlGaN已被确定为制造大功率电子器件和紫外光电器件的有前途的衬底材料。氢化物气相外延（HVPE）是一个很有前途的生长系统，它提供了高的生长速率。然而，关于AlN的HVPE的研究受到限制，因为AlCl作为Al的源分子与夸脱（SiO_2）发生反应。通过热力学分析和实验发现，AlCl_3不与SiO_2发生反应，AlCl_3和NH_3为源气体时，AlN的HVPE是可能的。然后，我们尝试用HVPE体系生长AlN层。显示了蓝宝石衬底上AlN HVPE的成功。当HCl和NH_3的输入分压分别为6.0 × 10^<-3> atm和4 × 10^<-2> atm时，生长层（2.1μm厚度）的Aθ-2θ模式x射线衍射（XRD）谱图。此外，除了蓝宝石衬底引起的衍射峰外，只有与c轴取向六方AlN有关的衍射峰被观察到。接下来，我们对AlGaN三元合金HVPE生长的可能性进行了热力学分析。在AlGaN合金HVPE体系中，源分子为AlCl_3、GaCl和NH_3。以AiCl_3和GaCl为III族前驱体，对AlGaN的HVP进行了热力学分析。根据载气中氢气的输入比、温度和分压的取值范围，我们计算了AlGaN中AlN和GaN沉积的平衡分压和驱动力。结果表明，在低氢分压（载气中氢<10%）下，可控AlGaN HVPE是可能的。

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).