Diffused ZnO nanorod reflectors were designed and used in conventional flip-chip light-emitting diodes (FCLEDs) and FCLEDs with a flat reflector. The light output power and the light distribution of the resulting FCLEDs were improved by using the diffused ZnO nanorod reflectors owing to the light scattering of the roughened highly reflective Al metal and the low refractive ZnO nanorod array. Compared with the conventional FCLEDs and the FCLEDs with a flat reflector, the light output power was enhanced by 56.6 and 11.7% for the FCLEDs with a diffused 500-nm-long ZnO nanorod reflector, respectively. # 2012 The Japan Society of Applied Physics W ith the abundant technology progresses in epitaxial growth and device fabrication, GaN-based semiconductors have become promising materials for fabricating electronic devices, 1,2) optoelectronic devices, 3,4) and sensors. 5,6) Among them, light-emitting diodes (LEDs) have played an important role of economical and environmental devices owing to their prominent features such as smaller volume, longer lifetime, higher stability, and lower power consumption. To meet the requirement of high illumination efficiency, the extraction efficiency (EE) of the light emitted from the active layer of the devices is one of the key issues for GaN-based LEDs. In general, the light extraction efficiency is obstructed by the total internal reflection and the fresnel loss, which were originated from the large refractive index difference between the air (n air ¼ 1) and the GaN-based semiconductors (n GaN ¼ 2:4). To overcome these drawbacks, various methods, such as the use of a built-in reflector, 7,8) flip-chip (FC), 9,10) current spreading, 11,12) die shaping, 13,14) and surface roughness, 15,16) were reported previously. Among these methods, the one of using a built-in reflector exhibited inherent advantages including low cost, simple process, and outstanding light extraction improvement. Furthermore, the flip-chip lightemitting diodes (FCLEDs) with a diffused reflector possessed a better light extraction efficiency than the FCLEDs with a flat reflector. 17,18) In this work, to further improve the light extraction efficiency, the designed diffused nanorod reflector was used in FCLEDs. The diffused nanorod reflector was constructed using a highly reflective Al metal and a textured ZnO nanorod array with a smaller refractive index caused by the air void among the ZnO nanorods. 19) The epitaxial layers of the GaN-based LEDs were grown on c-plane sapphire substrates using a metal organic chemical vapor deposition (MOCVD) system. The structure consisted of a 50-nm-thick GaN buffer layer, a 3-m-thick Sidoped GaN layer (n ¼ 3 Â 10 17 cm À3 ), an undoped InGaNGaN multiple quantum well (MQW) active layer, a 50-nmthick Mg-doped Al 0:2 Ga 0:8 N layer (p ¼ 1 Â 10 17 cm À3 ), and a 300-nm-thick Mg-doped GaN layer (p ¼ 3 Â 10 17 cm À3 ). The InGaN-GaN MQW active layer consisted of ten periods of a 3-nm-thick In 0:23 Ga 0:77 N well layer and a 7-nm-thick GaN barrier layer. To activate the Mg-doped GaN lay...
Objective: The rapid changes in and development of information technology have made life convenient. Tablets are used in classrooms, allowing students to learn through digital games. This study aimed to explore the learning effects and learning interests of special education students, to whom a lively interactive digital game along with an appropriate course design were applied. Materials and Methods: This study applied the case study method to eight students with autism spectrum disorder (ASD) and cerebral palsy from a special education class in an elementary school. The effects of an interactive digital game on learning outcomes and learning interest (motivation/engagement) were analyzed through observation and documentation by the researchers. Results: The findings revealed that the composition of the special education students was highly heterogeneous, and the learning effect varied among individuals. The learning effect and time-series analyses on participants’ learning interest indicated more or fewer effects and outcomes in the eight participants. In addition to discovering the learning traits of each case, behavioral patterns and characters that differed from those in traditional teaching were observed for each participant, and involved some facets the researchers had never observed in other courses. In addition, the students with attention deficit hyperactivity disorder were observed to sit well on their seats to operate the game; they watched with concentration, and their eyes moved following the protagonist in the game. In addition to operating the tablets in their hands, they occasionally looked at other classmates to see the parts they were playing, and they were attentive to others. Conclusion: All of them could accomplish the mission by following game instructions, and their motivation and engagement significantly improved during the game.
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