Study Of Relation Between Microstructure And Optical Properties Of Low-dimension Semiconductor Materials (InGaN Quantum Well,InAs Quantum Dot)

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...