tailieunhanh - Báo cáo hóa học: " Selective area epitaxy of ultra-high density InGaN quantum dots by diblock copolymer lithography"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Selective area epitaxy of ultra-high density InGaN quantum dots by diblock copolymer lithography | Liu et al. Nanoscale Research Letters 2011 6 342 http content 6 1 342 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Selective area epitaxy of ultra-high density InGaN quantum dots by diblock copolymer lithography 1 11 2 2 1 Guangyu Liu Hongping Zhao Jing Zhang Joo Hyung Park Luke J Mawst and Nelson Tansu Abstract Highly uniform InGaN-based quantum dots QDs grown on a nanopatterned dielectric layer defined by selfassembled diblock copolymer were performed by metal-organic chemical vapor deposition. The cylindrical-shaped nanopatterns were created on SiNx layers deposited on a GaN template which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution. Scanning electron microscopy and atomic force microscopy measurements were conducted to investigate the QDs morphology. The InGaN GaN QDs with density up to 8 X 1010 cm-2 are realized which represents ultra-high dot density for highly uniform and well-controlled nitride-based QDs with QD diameter of approximately 22-25 nm. The photoluminescence PL studies indicated the importance of NH3 annealing and GaN spacer layer growth for improving the PL intensity of the SiNx-treated GaN surface to achieve high optical-quality QDs applicable for photonics devices. Introduction Nitride-based semiconductor devices have tremendous applications in solid-state lighting 1-9 lasers 10-14 photovoltaic 15-17 thermoelectricity 18-20 and terahertz photonics 21 22 . Nitride-based InGaN quantum wells QWs are typically employed as active regions in energy-efficient and reliable light-emitting diodes LEDs for solid-state lighting. However the large spontaneous and piezoelectric polarization fields in III-Nitride material lead to a significant charge separation effect 23-35 which in turn results in low internal quantum efficiency of green-emitting nitride-based LEDs and high threshold current density in nitride lasers. Nonpolar nitrides were .