【作者】 吕威；

【导师】 陈岗； 张泽；

【作者基本信息】 吉林大学 ， 材料物理与化学， 2005， 博士

【摘要】 本文利用透射电子显微镜、光致发光谱、X 射线双晶衍射和电子全息等多种实验手段和方法,深入地研究了二维InGaN/GaN 多量子阱结构差异对光学性质的影响,以及具有InGaAs/InAlAs 复合盖帽层的InAs 量子点快速热退火过程中结构和光学性质的演化及其机理。主要结果如下:研究了光学性能差异较大的InGaN/GaN 多量子阱材料,发现:在性能较差的样品中,从InGaN 应力层中产 ?生了高密度的Burgers 矢量为b=1/3<1120>类型的纯刃型位错失配位错,这些失配位错是由于应力层厚度超过临界厚度产生应力弛豫引起的。通过光致发光方法研究了经过应力弛豫和未发生弛豫的InGaN 量子阱样品的发光性能,发现两类样品发光强度相差较大,由于弛豫所产生的位错对于样品的发光性能有很大的影响,是发光性能衰减的主要原因。将我们的实验结果与已有的理论模型进行综合分析对比发现,我们的实验结果完全符合Fischer 模型,说明Fischer 等提出的模型可以用来预测InxGa1-xN/GaN 量子阱结构的应变弛豫临界厚度。通过电子全息方法得到的相位重构图中,我们观察到未发生应力弛豫的阱与垒间的界面很清晰,量子阱形态很完整;已产生弛豫的阱(InGaN 层)沿[0001]生长方向的上表面(应力层与盖帽层间的界面)非常模糊,难以确定;说明应力弛豫对量子阱的阱深改变影响不是很大,主要是破坏了界面尤其是上层界面的平整度,导致发光性能很差。利用光致发光方法和高分辨电镜分析了具有InGaAs/InAlAs 复合盖帽层的InAs 量子点不同温度退火后光学和结构演化行为。研究发现850 C 退火之后, o量子点层和复合覆盖层结构互相扩散形成了InAlGaAs 单量子阱,这种结构导致与原来的量子点样品比较,PL 峰的位置蓝移了370meV,半高宽得到很大改善并且强度增加了近2.7 倍。更多还原

【Abstract】 The growth and research of structural and optical properties of low-dimensionnanometer materials is one of the frontiers of semiconductor science, due to thepossibility of the creation of new optoelectronic devices based on them. In this thesis,the effect of structural difference on optical properties of InGaN/GaN multiplequantum wells and the Influence of the rapid thermal annealing temperature on theoptical and structural properties of InAs quantum dots have been investigated bytransmission electron (TEM) 、photoluminescence (PL) 、double crystal x-raydiffraction (DCXRD)、electron holography (EM) etc. Results are summaried asfollowed:(1) InxGa1-xN/GaN multiple quantum well samples with strained-layer thicknesslarger/less than the critical thickness were investigated. For the sample withstrained-layer thicknesses greater than the critical thicknesses, a high density of pureedge type threading dislocations generated from MQW layers and extended to the caplayer was observed. But for the sample with strained-layer thicknesses less than thecritical thicknesses, it has no such phenomenon. These dislocations result fromrelaxation of the strained-layers when their thicknesses are beyond the criticalthicknesses. It is found that the misfit dislocations generated from strain relaxation areall pure-edge threading dislocations with burgers vectors of b =1/3<11 0>. Therelaxation of strained layer was mainly achieved by the formation of dislocationschanged their slip planes from {0001} to {1010}.(2) InxGa1-xN/GaN multiple quantum well samples with strained-layer thicknesslarger/less than the critical thickness were investigated by temperature-dependentphotoluminescence. PL results show that the PL intensity of sample withstrained-layer thicknesses greater than the critical thicknesses decreases fast with theincreasing temperature. At room temperature, the emission peak related to band-edgeemission was almost depressed by the broad yellow band with an intensity maximumat 2.28ev, but both samples show well PL efficiency at the low temperature. The更多还原