Transmission Electron Microscopy Studies on InGaN/GaN Multiple Quantum-well Structures with Different Presrain Conditions
Date Issued
2007
Date
2007
Author(s)
Cheng, Chia-Feng
DOI
en-US
Abstract
for growing the five QWs in the control sample. Besides, the GaN barrier layers of different thicknesses right above the low-indium QW are deposited among the three samples. We use the techniques of high-resolution
transmission electron microscopy (HRTEM) and strain
state analysis (SSA) to analyze the nanostructures of these four samples. From the HRTEM images, one can see different degrees of indium aggregation and composition fluctuation between QWs are observed. From the calibrations of the average indium contents of those QWs based on the SSA images, it is found that the QWs closer to the low-indium one have higher indium contents. Such an increase of indium incorporation is attributed to the pre-strain effect of the low-indium QW on the barrier layer right above it. Also, we found that the pre-strain effect diminishes along the growth of more QWs. In the comparison of optical property in these four samples, one can see that the light-emitting wavelengths in each sample are all around 500nm. Also, we find that the smaller the thickness of the pre-strained layer in the LED is, the smaller the blue shift in wavelength induced by the increase of current injection becomes.
Subjects
多重量子井
穿透式電子顯微術
預施應力
藍移
Multiple-Quantum Well (MQW)
Transmission Electron Microscopy (TEM)
Prestrain
Blue-Shift
Type
thesis
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