• Title/Summary/Keyword: Bird's-Eye View

Search Result 59, Processing Time 0.029 seconds

Human Detection and Fuzzy Temperature Control System for Energy Reduction of Cooling Device in Elevator (승강기용 냉각장치의 에너지 절감을 위한 사람 검출과 퍼지 온도 제어 시스템)

  • Eum, Hyukmin;Jang, Sukyoon;Lee, Heejin;Park, Mignon;Yoon, Changyong
    • Journal of the Korean Institute of Intelligent Systems
    • /
    • v.25 no.2
    • /
    • pp.147-154
    • /
    • 2015
  • In this paper, we propose human detection and fuzzy temperature control system for energy reduction of cooling device in elevator. In order to improve problems of existing cooling device using the refrigerant, energy reduction and efficient management are continuously achieved because of operation of thermoelectric cooling device using the human detection and fuzzy temperature control system. The proposed system confirms the number of passengers in elevator and temperature is then controlled by those numbers and an average temperature for the season in fuzzy system. The human detection method scans the number of passengers using a head part as a feature based on bird's-eye view camera in elevator. The fuzzy system determines elevator internal temperature considering atmospheric temperature and the scanned passenger numbers as a look-up table. The proposed system reduces energy of the cooling device through the human detection and temperature control. In experiment, energy reduction is confirmed and the performance of the proposed system is verified.

Estimating vegetation index for outdoor free-range pig production using YOLO

  • Sang-Hyon Oh;Hee-Mun Park;Jin-Hyun Park
    • Journal of Animal Science and Technology
    • /
    • v.65 no.3
    • /
    • pp.638-651
    • /
    • 2023
  • The objective of this study was to quantitatively estimate the level of grazing area damage in outdoor free-range pig production using a Unmanned Aerial Vehicles (UAV) with an RGB image sensor. Ten corn field images were captured by a UAV over approximately two weeks, during which gestating sows were allowed to graze freely on the corn field measuring 100 × 50 m2. The images were corrected to a bird's-eye view, and then divided into 32 segments and sequentially inputted into the YOLOv4 detector to detect the corn images according to their condition. The 43 raw training images selected randomly out of 320 segmented images were flipped to create 86 images, and then these images were further augmented by rotating them in 5-degree increments to create a total of 6,192 images. The increased 6,192 images are further augmented by applying three random color transformations to each image, resulting in 24,768 datasets. The occupancy rate of corn in the field was estimated efficiently using You Only Look Once (YOLO). As of the first day of observation (day 2), it was evident that almost all the corn had disappeared by the ninth day. When grazing 20 sows in a 50 × 100 m2 cornfield (250 m2/sow), it appears that the animals should be rotated to other grazing areas to protect the cover crop after at least five days. In agricultural technology, most of the research using machine and deep learning is related to the detection of fruits and pests, and research on other application fields is needed. In addition, large-scale image data collected by experts in the field are required as training data to apply deep learning. If the data required for deep learning is insufficient, a large number of data augmentation is required.

Study on the Painting of Gyeongwoo-gung Shrine (景祐宮圖) (국립문화재연구소 소장 '경우궁도(景祐宮圖)'에 관한 연구)

  • Kim, Kyung Mee
    • Korean Journal of Heritage: History & Science
    • /
    • v.44 no.1
    • /
    • pp.196-221
    • /
    • 2011
  • The Royal Private Shrines or the Samyo(私廟), were dedicated to members of Choseon's royal family who could not be enshrined at the (official) Royal Ancestral Shrine, the Jongmyo(宗廟). The Samyo were constructed at the national level and were systematically managed as such. Because these private Shrines were dedicated to those who couldn't belong to the Jongmyo but were still very important, such as the ruling king's biological father or mother. The details of all royal constructions were included in the State Event Manuals, and with them, the two-dimensional layouts of the Samyo also. From the remaining "Hyunsa-gung Private Tomb Construction Layout Record(顯思宮別廟營建都監儀軌)" of 1824, which is the construction record of Gyeongwoo-gung Shrine(景祐宮) dedicated to Subin, the mother of King Sunjo(純祖), it became possible to investigate the so far unknown "The Painting of Gyeongwoo-gung Shrine", in terms of the year produced, materials used and other situational contexts. The investigation revealed that the "The Painting of Gyeongwoo-gung Shrine" is actually the "Hyunsa-gung Private Tomb Layout" produced by the Royal Construction Bureau. The bureau painted this to build Hyunsa-gung Private Shrine in a separately prepared site outside the court in 1824, according to the royal verdict to close down and move the temporary shrine inside the courtyard dedicated to Subin who had passed away in 1822. As the Construction Bureau must have also produced the Gyeongwoo-gung Shrine Layout, the painter(s) of this layout should exist among the official artists listed in the State Event Manual, but sadly, as their paintings have not survived to this day, we cannot compare their painting styles. The biggest stylistic character of the Painting of Gyeongwoo-gung Shrine is its perfect diagonal composition method and detailed and neat portrayalof the many palace buildings, just as seen in Donggwoldo(東闕圖, Painting of a panoramic view for Changdeokgung and Changgyeonggung Palaces). A well-perceiving architectural painting employs a specific point of view chosen to fit the purpose of the painting, or it can opt to the multi-viewpoint. Korean traditional architectural paintings in early ages utilized the diagonal composition method, the bird-eye viewpoint, or the multi-viewpoint. By the 18th century, detailed but also artistic architectural paintings utilizing the diagonal method are observed. In the early 19th century, the peak of such techniques is exhibited in Donggwoldo(Painting of a panoramic view for Changdeokgung and Changgyeonggung Palaces). From the perfect diagonal composition method employed and the details of the palace buildings numbering almost two hundreds, we can determine that the Painting of Gyeongwoo-gung Shrine also belongs to the same category of the highly technical architectural paintings as Donggwoldo(Painting of a panoramic view for Changdeokgung and Changgyeonggung Palaces). We can also confirm this hypothesis by comparing the painting techniques employed in these two paintings in detailthe way trees and houses are depicted, and the way ground texture is expressed, etc. The unique characteristic of the Painting of Gyeongwoo-gung Shrine is, however, that the area surrounding the central shrine building(正堂), the most important area of the shrine, is drawn using not the diagonal method but the bird-eye viewpoint with the buildings lying flat on both the left and right sides, just as seen in the "Buildings Below the Central Shrine(正堂以下諸處)" in the State Event Manual's Painting Method section. The same viewpoint method is discovered in some other concurrent paintings of common residential buildings, so it is not certain that this particular viewpoint had been a distinctive feature for shrine paintings in general. On the other hand, when the diagonalmethod pointing to the left direction is chosen, the top-left and bottom-right sections of the painting become inevitably empty. This has been the case for the Painting of Gyeongwoo-gung Shrine, but in contrast, Donggwoldo shows perfect screen composition with these empty margins filled up with different types of trees and other objects. Such difference is consistent with the different situational contexts of these two paintings: the Painting of Gyeongwoo-gung Shrine is a simple single-sheet painting, while Donggwoldo is a perfected work of painting book given an official title. Therefore, if Donggwoldo was produced to fulfill the role of depiction and documentation as well as the aesthetic purpose, contrastingly, the Painting of Gyeongwoo-gung Shrine only served the purpose of copying the circumstances of the architecture and projecting them onto the painting.

A Study on Jeong Su-yeong's Handscroll of a Sightseeing Trip to the Hangang and Imjingang Rivers through the Lens of Boating and Mountain Outings (선유(船遊)와 유산(遊山)으로 본 정수영(鄭遂榮)의 《한임강유람도권》 고찰)

  • Hahn, Sangyun
    • MISULJARYO - National Museum of Korea Art Journal
    • /
    • v.96
    • /
    • pp.89-122
    • /
    • 2019
  • In this paper, I argue that the Handscroll of a Sightseeing Trip to the Hangang and Imjingang Rivers by Jeong Su-yeong (1743~1831, pseudonym: Jiwujae) is a record of his private journeys to several places on the outskirts of Hanyang (present-day Seoul) and that it successfully embodies the painter's subjective perspective while boating on these rivers and going on outings to nearby mountains. Around 1796, Jeong Su-yeong traveled to different places and documented his travels in this 16-meter-long handscroll. Several leaves of paper, each of which depicts a separate landscape, are pieced together to create this long handscroll. This indicates that the Handscroll of a Sightseeing Trip to the Hangang and Imjingang Rivers reflected the painter's personal subjective experiences as he went along his journey rather than simply depicts travel destinations. The Handscroll of a Sightseeing Trip to the Hangang and Imjingang Rivers features two types of travel: boating and mountain outings on foot. Traveling by boat takes up a large portion of the handscroll, which illustrates the channels of the Hangang and Imjingang Rivers. Mountain outings correspond to the sections describing the regions around Bukhansan, Gwanaksan, and Dobongsan Mountains. Jeong Su-yeong traveled to this wide span of places not just once, but several times. The fact that the Hangang River system are not presented in accordance with their actual locations shows that they were illustrated at different points. After visiting the riversides of the Hangang and Namhangang Rivers twice, Jeong Su-yeong delineated them in fourteen scenes. Among them, the first eight illustrate Jeong's initial trip by boat, while the other six scenes are vistas from his second trip. These fourteen scenes occupy half of this handscroll, indicating that the regions near the Hangang River are painted most frequently. The scenes of Jeong Su-yeong's first boating trip to the system of the Hangang River portray the landscapes that he personally witnessed rather than famous scenes. Some of the eight scenic views of Yeoju, including Yongmunsan Mountain, Cheongsimru Pavilion, and Silleuksa Temple, are included in this handscroll. However, Jeong noted spots that were not often painted and depicted them using an eye-level perspective uncommon for illustrating famous scenic locations. The scenes of Jeong's second boating trip include his friend's villa and a meeting with companions. Moreover, Cheongsimru Pavilion and Silleuksa Temple, which are depicted in the first boating trip, are illustrated again from different perspectives and in unique compositions. Jeong Su-yeong examined the same locations several times from different angles. A sense of realism is demonstrated in the scenes of Jeong's first and second boating trips to the channels of the Hangang River, which depict actual roads. Furthermore, viewers can easily follow the level gaze of Jeong from the boat. The scenes depicting the Imjingang River begin from spots near the Yeongpyeongcheon and Hantangang Rivers and end with places along the waterways of the Imjingang River. Here, diverse perspectives were applied, which is characteristic of Imjingang River scenes. Jeong Su-yeong employed a bird's-eye perspective to illustrate the flow of a waterway starting from the Yeongpyeongcheon River. He also used an eye-level perspective to highlight the rocks of Baegundam Pool. Thus, depending on what he wished to emphasize, Jeong applied different perspectives. Hwajeogyeon Pond located by the Hantangang River is illustrated from a bird's-eye perspective to present a panoramic view of the surroundings and rocks. Similarly, the scenery around Uhwajeong Pavilion by the Imjingang River are depicted from the same perspective. A worm's-eye view was selected for Samseongdae Cliff in Tosangun in the upper regions of the Imjingang River and for Nakhwaam Rock. The scenes of Jeong Su-yeong's mountain outings include pavilions and small temple mainly. In the case of Jaeganjeong Pavilion on Bukhansan Mountain, its actual location remains unidentified since the pavilion did not lead to the route of the boating trip to the system of the Hangang River and was separately depicted from other trips to the mountains. I speculate that Jaeganjeong Pavilion refers to a pavilion either in one of the nine valleys in Wooyi-dong at the foot of Bukhansan Mountain or in Songajang Villa. Since these two pavilions are situated in the valleys of Bukhansan Mountain, their descriptions in written texts are similar. As for Gwanaksan Mountain, Chwihyangjeong and Ilganjeong Pavilions as well as Geomjisan Mountain in the Bukhansan Mountain range are depicted. Ilganjeong Pavilion was a well-known site on Gwanaksan that belonged to Shin Wi. In this handscroll, however, Jeong Su-yeong recorded objective geographic information on the pavilion rather than relating it to Shin Wi. "Chwihyangjeong Pavilion" is presented within the walls, while "Geomjisan Mountain" is illustrated outside the walls. Handscroll of a Sightseeing Trip to the Hangang and Imjingang Rivers also includes two small temples, Mangwolam and Okcheonam, on Dobongsan Mountain. The actual locations of these are unknown today. Nevertheless, Gungojip (Anthology of Gungo) by Yim Cheonsang relates that they were sited on Dobongsan Mountain. Compared to other painters who stressed Dobong Seowon (a private Confucian academy) and Manjangbong Peak when depicting Dobongsan Mountain, Jeong Su-yeong highlighted these two small temples. Jeong placed Yeongsanjeon Hall and Cheonbong Stele in "Mangwolam small temple" and Daeungjeon Hall in front of "Okcheonam small temple." In addition to the buildings of the small temple, Jeong drew the peaks of Dobongsan Mountain without inscribing their names, which indicates that he intended the Dobongsan peaks as a background for the scenery. The Handscroll of a Sightseeing Trip to the Hangang and Imjingang Rivers is of great significance in that it embodies Jeong Su-yeong's personal perceptions of scenic spots on the outskirts of Hanyang and records his trips to these places.

The Visual Aesthetics of Drone Shot and Hand-held Shot based on the Representation of Place and Space : focusing on World Travel' Peninsula de Yucatán' Episode (장소와 공간의 재현적 관점에서 본 드론 쇼트와 핸드헬드 쇼트의 영상 미학 : <세계테마기행> '유카탄 반도'편을 중심으로)

  • Ryu, Jae-Hyung
    • Journal of Korea Entertainment Industry Association
    • /
    • v.14 no.3
    • /
    • pp.251-265
    • /
    • 2020
  • The Drone shot is moving images captured by a remotely controlled unmanned aerial vehicle, takes usually bird's eye view. The hand-held shot is moving images recorded by literal handheld shooting which is specialized to on-the-spot filming. It takes a walker's viewpoint through vivid realism of its self-reflexive camera movements. The purpose of this study is to analyze comparatively aesthetic functions of the drone shot and the hand-held shot. For this, the study understood Certeau's concepts of 'place' and 'space,' chose World Travel 'Peninsula de Yucatan' episode as a research object, and analytically applied two concepts to the scenes clearly presenting two shots' aesthetic characteristics. As a result, the drone shot took the authoritative viewpoint providing the general information and atmosphere as it overlooked the city with silent movements removing the self-reflexivity. This aesthetic function was reinforced the narration and subtitles mediating prior-knowledge about proper rules and orders of the place. The drone shot tended to project the location as a place. Conversely, the hand-held shot practically experienced the space with free walking which is free from rules and orders inherent in the city. The aesthetics of hand-held images represented the tactic resisting against the strategy of a subject of will and power in that the hand-held shot practiced anthropological walking by means of noticing everyday lives of the small town and countryside than main tourist attraction. In opposition to the drone shot, the hand-held shot tended to reflect the location as a space.

The Way of Expression of Wangreungdo(王陵圖: A Kind of A Royal Mausoleum Map) Reflected on Sanhyoungdo(山形圖: A Kind of A Mountain Map) in the Late Nineteenth Century - Centering the Drawings Relevant to Jogyoungdan(肇慶壇) of Lee Han, the Founder of Jeonju Lee Family - (19세기 후반 산형도(山形圖)로 본 왕릉도(王陵圖)의 표현방법(表現方法) -전주이씨(全州李氏) 시조(始祖) 이한(李翰)의 조경단(肇慶檀) 관련 그림을 중심으로-)

  • Kim, Jeong-Moon
    • Journal of the Korean Institute of Traditional Landscape Architecture
    • /
    • v.30 no.1
    • /
    • pp.57-65
    • /
    • 2012
  • This work attempted to study the properties of expression of ground, the composition of outlook and the implications of the connotative symbolic scenery throughout investigating the properties of expression content and method of the scenery, outlook, viewpoint, natural features for each drawing and intention of making 4 old maps, which had been made in the period of the Great Korean Empire and had been called 'Wansan-dohyoung(完山圖形),' 'Jogyeongdan- bigak-jaesil-dohyoung(肇慶壇碑閣齋室圖形),' 'Jeonju-geonjisan-dohyoung(全州乾止山圖形)' and 'Jogyeongmyo-gyounggijeon-dohyoung(肇慶廟慶基殿圖形),' and analyzing the correlation between their drawings. For this aim, observatory investigation by using a map, on-spot investigation, analysis involving the satellite images and internet were carried out with literature review simultaneously. The result of investigation could be sum up as follows. Gyounggijeon(1410), Jogyeongmyo(1771) and Jogyeongdan(1899), where are the core space to lay the historically firm foundation for securing the fact Jeonju is the home of the Royal Family of Joseon, had been built, fixed and extended for giving legitimacy to the Joseon Dynasty and a part of strengthening of royal authority. And these had played an important role of spiritual mainstay from early in the Joseon Dynasty to the era of the Great Korean Empire and had been managed and maintained continuously. It is grasped that the 4 maps consist of Sanhyuoungdo(山形圖; a kind of a mountain map), which is the map for showing a burial place of Lee Han(李翰), the founder of the Joseon Dynasty, and its auxiliary drawings and these had been drawn intensively to justify dignity and authority of the Imperial Family and the Emperor after the name of country was renamed the Great Korean Empire as a part of national undertaking. In detail, Wansan-doghyoung is the key map for announcing the existence of Jogyeong-myo, Gyounggijeon and Jogyeongdan in Jeonju and informing their locations and Geonjisan-dohyoung is the map of divination based on topography for highlighting the geomantic justification of the founder's mausoleum. Jogyeongdan-bigak-jaesil-dohyooung is the partial map detailing for Geonjisan-dohyoung. Jeonju-geonjisan-dohyoung and Jogyeongmyo-gyounggijeon-dohyoung had employed the binary reduced scale and the bird-eye view method and in the above maps, Geonji Mountain is the main mountain and these maps make an exaggeration of the main geographical features, centering Wangjabong and Euimyoso, unlike the real geographical features. Also, the other main geographical features, which are found in the burial place, are expressed in detail by changing the view. In the point of view of 1 set being consisted of 4 maps, 'Wansan-dohyoung' has the property not only as Gunhyoundo, which Gun and Hyoun mean a unit of the administrative district, respectively and Gynhyoundo is a kind of the map for recording their locations, but also as the map of showing their locations. On the other side, 'Jogyoungmyogyounggijeondohyoung' is a kind of lay-out drawing as a partially detailed map. In addition, it has been found out that 'Jeonju-geonjisan-dohyoung' and 'Jogyeongdan-bigak-jaesil-dohyoung' is not only Pungsu- hyounggukdo having the function of Sanhyoungdo but also a detail drawing. On the base of these properties, it is considered that the functionality as a serial map had been strengthened, unlike the existing old maps.

Landscape Gardening Culture in Late Joseon Dynasty Depicted in 'Ahoi-do' Paintings (아회도(雅會圖)에 나타난 조선후기 원림문화)

  • Lim, Eui-Je;So, Hyun-Su
    • Journal of the Korean Institute of Traditional Landscape Architecture
    • /
    • v.32 no.3
    • /
    • pp.46-57
    • /
    • 2014
  • This study contemplated the gardening culture from the pictures, which the scholars of late Joseon Dynasty, the aspects of garden landscapes and garden use behaviors are drawn as follows. 1. The yard by the detached house for men and guest in front of the premises(Sarang Madang) and backyard were the major places for Ahoi(social gatherings of the scholars). The mansions had interests in the management of the outer garden beyond the house wall with building structures like the pavilions on the high walls and side gates. This management and the selection of location anticipating in advance of the management are noteworthy. 2. Only house gardens had plant pots with flowers and the small flower bed(Hwa-O) at Sarang Madang occasionally had plant pots without flowers and oddly shaped stone pots and equipped pine branch eaves and traditional awnings made of plant material like a trellis. 3. The oddly shaped stones were significant landscape elements in the gardens of houses and villas. Some of them were depicted as the Taihu stone and this draws attention to the question of whether the Taihu stone was actually used in the garden of late Joseon Dynasty. 4. The gardens in villas accommodated the borrowed scenery with various materials like wooden fences, bamboo or reed fences, mud walls. They also had the artificial gardens with some odd shaped stones, old pines, bamboos, Japanese apricots, willows, paulownia trees, lotuses and plantains in the secured Madangs. 5. Gyeong Hwa Sa Jog(The scholars of the ruling class adapted to the 18th century's new historical aspect) of late Joseon Dynasty built the villas at the beautiful scenery closed to the their houses. 6. The Gardens around pavilions were located high closed to the mountain streams with nature like beautiful forests, oddly formed rocks, precipitous cliffs and viewing stones. The back side of the pavilion was enclosed by bamboo forests and the front had pines, ginkgoes and willows as shade trees. 7. The beautiful scenery which was preferred as the place for Ahoi was basically with fantastic peaks and precipitous cliffs which forms the distant view harmonized with a waterfall. Broad and flat rocks at the summit of a mountain which commands a bird's-eye view or on a mountain streamside with pine forest, willows and plum trees were chosen as the optimal places for Ahoi. 8. Pine trees were presumed to be more preferable than other species in the garden, especially an single planted old pine tree accented symbolism. 9. Portable tea braziers for boiling tea were adopted in all four types of the gardens. 10. The gardens mixed with auspicious landscape elements were the places of the arts for an unworldliness Ahoi through GeumGiSeoHwa(enjoying strings, go, writing and painting) and boiling tea.

A Study on the Landscape Structure and Meaning of Eight Scenic Views of Yeongsa-jeong Pavilion through the Painting and Poem (<영사정팔경도(永思亭八景圖)>와 팔영시로 본 영사정팔경의 경관구조와 의미)

  • Rho, Jae-Hyun;Son, Hee-Kyung;Kim, Hong-Kyun
    • Journal of the Korean Institute of Traditional Landscape Architecture
    • /
    • v.35 no.2
    • /
    • pp.58-68
    • /
    • 2017
  • The conclusion of this research after analyzing and interpreting the landscape structure and meaning of Yeongsajeongpalkyung (永思亭八景) that appears in Yeongsajeongpalyeongsi(永思亭八詠詩) of Cheonggye(靑溪) Yang, Dae-bak(梁大樸, 1544~1592) and through document studies, poetry and painting analysis and interpretation, and site investigation, is as follows. Yeongsajeong and its nearby lands are the area of "Yeongsa", where the builder, Ahn, Jeon(安?, 1518~1571) worshipped towards the grave of ancestors, and Yeongsajeongpalkyung oversees a family burial ground in Namwon, centering around Yeongsajeong such as Yocheon, Geumseokgyo and Cheonggyedong, and Sunjagang River and Mountain Jiri, which are the foot hold and key points of advantageous scenic views in Namwon. Yeongsajeongpalkyung, unlike general Jeongjapalkyung, shows a panoramic bird's-eye structure overseeing the landscape and scenery of the Yocheon area and Sunjagang River, in addition to Yeongsajeong, while show in a transition of location, a multi-view structure and time. The trace of visual unity with Sosangpalkyung of China can be seen in many places in Yeongsajeongpalkyung, which seems to be a transitional feature of composing poems regarding Palgyeong during the mid-Joseon dynasty, which pursues harmony with the local landscape of the Namwon area. The 'Changsongchwijuk(蒼松翠竹)' appearing in each of the first and second scenic views of Palgyeong and Yeongsajeongpalyeong can be understood as an incarnation of Yang, Dae-bak, the author of Palyeongsi or Ahn, Jeon, the builder of Yeongsajeong. On the other hand, as a result of interpreting the yin-yang features of poetic diction and picture elements appearing in the subtitle of Yeongsajeongpalyeong, Palyeongsi seems mostly full of yin-like elements and Palgyeongdo. Moreover, as a result of comparing and analyzing the acts expressed in and acts described in Yeongsajeongpalyeong, based on the fact that the reis almost no common ground between the two media except for Soongangmowoo, the third scenic view, the formal similarity between the two media can be acknowledged, however, it is difficult to discover any substantive 'integrity of poetry and painting'.

Efficient Red-Color Emission of InGaN/GaN Double Hetero-Structure Formed on Nano-Pyramid Structure

  • Go, Yeong-Ho;Kim, Je-Hyeong;Gong, Su-Hyeon;Kim, Ju-Seong;Kim, Taek;Jo, Yong-Hun
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2012.08a
    • /
    • pp.174-175
    • /
    • 2012
  • (In, Ga) N-based III-nitride semiconductor materials have been viewed as the most promising materials for the applications of blue and green light emitting devices such as light-emitting diodes (LEDs) and laser diodes. Although the InGaN alloy can have wide range of visible wavelength by changing the In composition, it is very hard to grow high quality epilayers of In-rich InGaN because of the thermal instability as well as the large lattice and thermal mismatches. In order to avoid phase separation of InGaN, various kinds of structures of InGaN have been studied. If high-quality In-rich InGaN/GaN multiple quantum well (MQW) structures are available, it is expected to achieve highly efficient phosphor-free white LEDs. In this study, we proposed a novel InGaN double hetero-structure grown on GaN nano-pyramids to generate broad-band red-color emission with high quantum efficiency. In this work, we systematically studied the optical properties of the InGaN pyramid structures. The nano-sized hexagonal pyramid structures were grown on the n-type GaN template by metalorganic chemical vapor deposition. SiNx mask was formed on the n-type GaN template with uniformly patterned circle pattern by laser holography. GaN pyramid structures were selectively grown on the opening area of mask by lateral over-growth followed by growth of InGaN/GaN double hetero-structure. The bird's eye-view scanning electron microscope (SEM) image shows that uniform hexagonal pyramid structures are well arranged. We showed that the pyramid structures have high crystal quality and the thickness of InGaN is varied along the height of pyramids via transmission electron microscope. Because the InGaN/GaN double hetero-structure was grown on the nano-pyramid GaN and on the planar GaN, simultaneously, we investigated the comparative study of the optical properties. Photoluminescence (PL) spectra of nano-pyramid sample and planar sample measured at 10 K. Although the growth condition were exactly the same for two samples, the nano-pyramid sample have much lower energy emission centered at 615 nm, compared to 438 nm for planar sample. Moreover, nano-pyramid sample shows broad-band spectrum, which is originate from structural properties of nano-pyramid structure. To study thermal activation energy and potential fluctuation, we measured PL with changing temperature from 10 K to 300 K. We also measured PL with changing the excitation power from 48 ${\mu}W$ to 48 mW. We can discriminate the origin of the broad-band spectra from the defect-related yellow luminescence of GaN by carrying out PL excitation experiments. The nano-pyramid structure provided highly efficient broad-band red-color emission for the future applications of phosphor-free white LEDs.

  • PDF