In this work, an InGaN-based, green micro-photonic crystal-light-emitting-diode (µ-PCLED), which incorporates a nanoporous, GaN-distributed Bragg reflector (DBR) to form a Fabry–Perot (FP) cavity, was fabricated and characterized. Simulations for the µ-PCLED’s optical features were systematically performed and analyzed. Numerical results revealed that the p-GaN photonic crystal (PC) with a filling factor of 0.3 is beneficial for improving the coupling constants of the first- and second-order Bragg diffractions. In addition, based on the product of quantum well (QW) and PC confinement factors, four to six pairs of InGaN QWs should be the preferable design. In order to achieve single-wavelength emission and small full-width at half-maximum (FWHM), the thickness of the n-GaN layer was controlled to be thinner than 920 nm, leading to more than 20 nm wavelength separation between two adjacent FP modes. Experimentally, the fabricated InGaN-based µ-PCLED with a mesa diameter of 30 µm can emit 545 nm green light with FWHM of about 10 nm and negligible blue-shift of about 3 nm in spontaneous emission under the injection current of 1 to 10 mA. Our simulation and experimental results demonstrate that the p-GaN PC design can effectively resolve the wavelength instability issue.
Learner autonomy has become a universally acknowledged benign notion and exercised in all levels of education, especially in tertiary settings, although some doubts have been cast on its suitability in teacher-dependent contexts. Learner autonomy entails capacity to take on responsibility for ones' own learning. This study aims to investigate students' perceptions of their own responsibility and their teachers', and then evaluate students' autonomy in English learning in an EAP curriculum in a Sino-British university in China. To these aims, a 30-item questionnaire was compiled to administer to 276 year 1 and year 2 students, and T-test and one-way ANOVA were used to analyze the data. It was found that students in this Sino-British context perceived themselves to assume more responsibility for their own learning compared to their Chinese counterparts, but teachers had more responsibility to stimulate their learning inside the classroom. The degree of autonomy increased accordingly by students' language proficiency level. Female students assumed more responsibility than male students while the latter were more autonomous than the former. Although students had a good understanding of course aims, they had low awareness of setting goals and plans. These findings have implications for promoting autonomy in tertiary settings in this specific context, as well as in other tertiary settings.
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