【摘要】 为了提高MOCVD外延硅基GaN材料的质量,在硅(111)衬底上以HT-A lN为缓冲层,在缓冲层上再生长变组份过渡层后外延生长GaN。过渡层为多层复合结构,分为高温变组分A lGaN、GaN、低温A lN、高温变组分A lGaN。在高温生长A lGaN和GaN层中插入一层低温生长A lN以缓解降温过程中应力对厚GaN层的影响,为了缓慢释放热应力、采用合适的慢降温工艺。当外延层的厚度小于1.7微米时GaN外延层无龟裂,而厚度不断增加时,GaN外延层产生龟裂。本文研究了A lN缓冲层生长温度、高温变组分A lGaN生长过程中生长时间的变化对所生长GaN材料的影响。采用三维视频显微镜、高分辨率双晶X射线衍射(DCXRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)和室温光致荧光光谱(RT-PL)对样品进行了测试分析。测试结果表明所研制的硅基GaN表面光亮、平整,过渡层的引入有利于降低外延层中应力,提高GaN结晶质量。更多还原

【Abstract】 High quality GaN films were grown on Si(111) substrates with high-temperature-grown AlN(HT-AlN) buffer layer and transitional layers by MOCVD.The transitional layers consist of composition gradual HT-AlGaN,HT-GaN,LT-AlN and HT-AlGaN,which were used to reduce the thermal strain during the cooling-down period.Furthermore,the process of low cooling speed was used to relax the thermal strain.A maximum crack-free thickness of 1.7μm was obtained for GaN on Si(111),but the crack is present with the increasing thickness.We have studied the influence of GaN growth parameters,such as growth temperature of AlN buffer and growth time of HT-AlGaN.The GaN layers were investigated by three-dimensional optical microscope,high resolving X-ray double crystal diffraction(DCXRD),scanning electron microscope(SEM),atomic force microscope(AFM) and room temperature photoluminescence(RT-PL).These results indicate that high quality GaN films with bright and smooth surface on the Si(111) can be improved by using the transitional layers,which reduce the thermal strain in the GaN layers.更多还原