Si衬底MOCVD生长GaN/InGaN多量子阱缺陷TEM研究

用透射电子显微镜对Si衬底生长GaN/InGaN多量子阱材料进行横断面测试,在衬底和缓冲层区域进行高分辨电子显微成像(HRTEM)、电子衍射衬度成像、选区电子衍射成像,在量子阱附近区域进行了双束近似电子衍衬像对其位错特性进行研究;用场发射扫描电子显微镜对饱和KoH溶液腐蚀前后材料成像.结果发现,AIN缓冲层具有多孔结构,高温GaN层位错平均密度达108cm-2,同扫描电子显微镜得到的六角腐蚀坑密度一致,量子阱以下发现大量位错发生90°弯曲,而使穿过量子阱位错密度大大降低.在线位错中,以刃位错居多,其次是混合位错,所观察区域几乎未见螺位错.

TEM Characterization of Defects in GaN/InGaN Multi-Quantum Wells Grown on Silicon by MOCVD

Transmission electron microscope (TEM) measurements performed on InGaN/GaN multiple-quantum-well (MQW) deposited Silicon substrates have been investigated.By taking high-resolution transmission electron microscopy (HRTEM) imagery,electron diffraction contrast imagery, and electron diffraction image in precincts between the Si substrate and the AlN buffer area,and also taking Two-beam electron diffract contrast imagery around the quantum well area,we have researched the characteristics of dislocation.In addition,we take the image of materials before and after saturated KOH solution’s cauterization by field emission scanning electric microscope(SEM).It is discovered that the AIN buffer layer is of porous structure,and that a great deal of incomplete dislocation parallel to the interface was found between the buffer layer and extension.The average density of dislocation reaches 1e8cm-2 in the high -temperature GaN layer,which is in accordance with the density of hexagonal etch pits by scanning electric microscope (SEM).Much dislocation below the quantum well was found to be so bent up to 90° that the dislocation density was reduced more through the quantum well.Moreover,edge dislocation accounts for the largest part among all the line dislocations,and mixed dislocation is second,but screw dislocation is hardly found in the observed area.Therefore,we conclude that the porous structure of low-temperature ALN buffer’s enables the extension layer to develop under the ELO model,which leads to a massive dislocation bend below the quantum well and then the density of the penetrating dislocation is reduced.