Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Improving the emission efficiency of MBE-grown GaN/AlN QDs by strain control | Niu et al. Nanoscale Research Letters 2011 6 611 http content 6 1 611 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Improving the emission efficiency of MBE-grown GaN AlN QDs by strain control Lang Niu Zhibiao Hao Jiannan Hu Yibin Hu Lai Wang and Yi Luo Abstract The quantum-confined stark effect induced by polarization has significant effects on the optical properties of nitride heterostructures. In order to improve the emission efficiency of GaN AlN quantum dots QDs a novel epitaxial structure is proposed a partially relaxed GaN layer followed by an AlN spacer layer is inserted before the growth of GaN QDs. GaN AlN QD samples with the proposed structure are grown by molecular beam epitaxy. The results show that by choosing a proper AlN spacer thickness to control the strain in GaN QDs the internal quantum efficiencies have been improved from to and from to for QDs emitting violet and green lights respectively. Keywords GaN QDs quantum-confined stark effect internal quantum efficiency Introduction Recently with progress in the growth of high-quality bulk AlN 1 2 a lot of efforts have been devoted to GaN AlN quantum dots QDs because of their unique properties such as broad emission wavelength range covering the whole visible light which provides a promising way to achieve white light-emitting diodes LEDs 3 . Besides the large conduction band offset approximately 2 eV for GaN AlN offers a prospect to cover the fiber optical telecommunication wavelength range to pm by intersubband transition 4 5 . By controlling the growth conditions the sizes and densities of the GaN AlN QDs can be varied and the photoluminescence PL wavelength can also be tuned. However the large lattice mismatch between GaN and AlN and their polarization properties induce a strong built-in electric field causing a remarkable quantum-confined stark effect QCSE which reduces the internal quantum efficiency IQE of the
