Epitaxial Growth of High Quality SiC by Sublimation Close Space Technique with High Growtn Rate

在CST法中，在由源、衬底和石墨间隔物构成的狭窄空间中，通过升华和扩散转移来促进生长。该方法与传统的碳化硅块材升华法基本相同。配置的一大不同是源和衬底之间的距离。我们采用高纯度的3C-SiC多晶片作为源，在2200-2400ﾟ℃的温度范围内实现了高生长，其生长速度与温度的关系得到的激活能为147kcal/m/h。通过在衬底上引入偏转角，在较宽的温度范围内获得了镜面状的形貌。观察到阶梯状聚束现象，台阶的迹线宽度约为5微米，沿&lt；1120&gt；方向观察到有线状阴影的缺陷，表明晶体的生长遵循阶梯流动机制。表面形貌通常受许多参数的影响，如间隔层高度。当间隔物高度减小时，出现波浪形。随着高度的增加，表面变得相当光滑。此外，还使用了Ta-Sheet，以防止坩埚壁上产生不需要的碳化物。合适的工艺条件可以获得非常光滑的表面，但Ta的碳化处理似乎是获得高质量碳化硅外延层的关键参数。在Ta粘贴坩埚中制备的外延层，获得了阶跃聚束自由表面。在光致发光测量中，施主-受体对的发射被大大抑制。在光致发光中，观察到了与中性N施主结合的激子有关的RO和SO线。这意味着外延层是高质量的。特别是观察到了高生长速率的外延层，如100µm/h以上，这表明提高生长速率有助于降低外延层中的杂质浓度。我们制作的肖特基二极管的击穿电压为40V，没有边缘端子。

In CST method, growth is promoted by sublimation and diffusion transfer in a narrow space which is constructed by source, substrate and graphite spacer. This method is basically same as conventional sublimation method for SiC-bulk. One big difference of configuration is the distance between source and substrate. We used 3C-SiC polycrystalline plate with high purity as source and High growth was achieved at a temperature range of 2200-2400ﾟC, and it was around 40-200 mu m/h. Activation energy obtained by temperature dependence of the growth rate was l47kcal/mol. By introducing off-angle to the substrate, a mirror-like morphology was obtained in the wide temperature range. Step bunching was also observed and trace width of the step was about 5 mu m. A defect having line shaped shadow was observed along <1120> direction, and it indicates that crystal growth followed step-flow mechanism. Surface morphology is often affected by many parameters such as spacer height. When the spacer height decreased, wavy pattern appeared. When the height increased, rather smooth surface appeared. Ta-sheet was also used to avoid unwanted carbon species from the wall of crucible. Appropriate condition, very smooth surface was obtained, however, carbonization of Ta seems a key parameter to get high quality SiC epilayer. Epilayer made in Ta pasted crucible, step-bunching free surface was obtained. Donor-acceptor pair emission was greatly suppressed in the photoluminescense measurement In this photoluminescence, RO and So lines, which is related excitons bound to neutral N donors, were observed. It means epitaxial layers are of high quality. These lines were especially observed epitaxial layers with high growth rate such as more than 100 mu m/h. It indicates that increasing growth rate may be useful to decrease impurity density doped into epitaxial layers. We made Schottky diodes showed breakdown voltage of 40V without edge termination.