a Department of Physics, Xiamen University, Xiamen 361005, China;
b Pen-Tung Sah Institute of Micro-Nano Science and Technology, Xiamen University, Xiamen 361005, China;
c Department of Electronic Engineering, Xiamen University, Xiamen 361005, China
Abstract The structural and optical properties of InGaN/GaN multiple quantum wells (MQWs) with different barrier thicknesses are studied by means of high resolution X-ray diffraction (HRXRD), a cross-sectional transmission electron microscope (TEM), and temperature-dependent photoluminescence (PL) measurements. HRXRD and cross-sectional TEM measurements show that the interfaces between wells and barriers are abrupt and the entire MQW region has good periodicity for all three samples. As the barrier thickness is increased, the temperature of the turning point from blueshift to redshift of the S-shaped temperature-dependent PL peak energy increases monotonously, which indicates that the localization potentials due to In-rich clusters is deeper. From the Arrhenius plot of the normalized integrated PL intensity, it is found that there are two kinds of nonradiative recombination processes accounting for the thermal quenching of photoluminescence, and the corresponding activation energy (or the localization potential) increases with the increase of the barrier thickness. The dependence on barrier thickness is attributed to the redistribution of In-rich clusters during the growth of barrier layers, i.e., clusters with lower In contents aggregate into clusters with higher In contents.
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 61106044 and 61274052), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110121110029), the Fundamental Research Funds for the Central Universities of Ministry of Education of China (Grant No. 2013121024), and the Natural Science Foundation of Fujian Province of China (Grant No. 2013J05096).
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