侧向外延法生长的高质量GaN及其外延缺陷的观察(英文)

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

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SiO2 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 108 cm-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GaN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GaN中的晶格失配应力已被部分释放。

High quality GaN is grown by epitaxial lateral overgrowth(ELO) technique on SiO_(2~)-patterned GaN “template”. The results from luminescence microscope observation reveal that nucleation happens on the SiO_2 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 SiO_2 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 10~8 cm^(-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.