侧向外延法生长的高质量GaN及其外延缺陷的观察

在有条状SiO2图形的GaN“模板”上，侧向外延方法生长了高质量的GaN。荧光显微镜的结果表明在SiO2掩膜区有成核过程发生。原因可能是SiO2的质量不高，为GaN的生长提供了一些成核中心。在GaN层的厚度达到4．5μm后，侧向的融合开始发生。侧向生长的速度与垂直生长速度几乎相同。在所有的SiO：掩膜上方都形成了空洞。样品在240℃熔融的KOH中腐蚀13min。在SiO2掩膜区生长的GaN，其腐蚀坑密度(相当于穿透位错密度)减少到几乎为零。而在窗口区生长的GaN，腐蚀坑密度仍然很高，达到10^8cm^-2量级。同时，我们发现具有不同窗口尺寸的样品在SiO2掩膜区上侧向生长的CaN的晶体质量基本相同，与窗口区的宽度几乎无关。室温光荧光结果表明侧向外延法生长的CaN中的晶格失配应力已被部分释放。

High Quality GaN Grown by Epitaxial Lateral Overgrowth Technique and Epitaxial Defects Observation

High quality GaN is grown by epitaxial lateral overgrowth(ELO) technique on SiO2-pattemed GaN "template". The results from luminescence microscope observation reveal that nucleation happens on the SiO2 mask. After the thickness reaches about 4.5 μm, the coalescence starts. The lateral growth rate is almost the same as the vertical growth rate. Voids are formed on all of the SiO2 mask area. ELO GaN is etched in molten KOH for 13 min at 240 ℃.The threading dislocation density is reduced to almost zero in the area on mask. And the threading dislocation density is still high in the area on windows. It is the order of 108cm-2. Also we found that the qualities in masks area for samples with different window area size are similar and have no relation with window area size. The room temperature photoluminescence (PL) results indicate that the stress in ELO GaN has been released partially.