연구실구성원 연구책임자 : 박성주교수 박사과정 : 임재홍김백현박일규권민기황대규조창희오민석김상균김자연박태영오재석 석사과정강창구서승범이기성최용석문진수조주영 발행인 : 박성주 편집인 : 조창희 2006.4.28 제 11 호 삼성전자 -LG 필립스 LCD ' 맞불 ' 삼성전자와 LG 필립스 LCD 가 LED 를광원으로사용하는 TV 용 LCD 패널주도 권경쟁에돌입했다. 삼성전자와 LG 필립스 LCD 는기존냉음극형광램프 (CCFL) 방식의기존백라이트유닛 (BLU) 을발광다이오드 (LED) BLU 로대체한 TV 용 LCD 패널을하반기에본격적으로선보일계획이다. 이에따라하반기이후 LED BLU 를채택한 TV 용 LCD 패널상용화가급물살을탈전망이다. 삼성전자와 LG 필립스 LCD 는 LED 를광원으로사용하면기존 CCFL 방식에비 해색재현율이크게높아지고수은이사용되지않아각종환경규제에유리 할뿐만아니라공정또한단순화할수있을것으로전망했다. 또대형 LCD 패널의고효율 고화질영상구현등제품경쟁력제고에도적잖은영향을끼칠 것으로내다보고있다. 삼성전자 (LCD 총괄 ) 는하반기에 LED BLU 를채택한 대형 TV 용패널을출시할계획이다. 그간일본소니의요청에따라 LED BLU 를채택한 32 인치와 40 인치 46 인치등대형 TV 용패널을생산 제공한삼성전 자는자체모델을준비중이다. 조용덕삼성전자 LCD 총괄상무는 LED BLU 를채택한모니터용패널은물론대형 TV 용패널개발을이미완료했다 며 하반기이후삼성전자고유의 TV 용패널을선보일예정 이라고말했다. LG 필립스 LCD 또한 LED BLU 를채택한대형 TV 용 LCD 패널을출시할예정이 다. LG 필립스 LCD 는이미 LED BLU 를채택, 110% 이상의색재현율과최고 1 만대 1 의명암비의우수한영상표현이가능한세계최대크기의 47 인치 LCD 패널을개발한바있다. 이영득전략담당상무는 LED BLU 를사용한 TV 용 LCD 패널은이미개발이완료됐지만아직은비용이문제 라며 협력업체 와비용절감을위해공조, 하반기 LED BLU 를채택한대형 TV 용패널을출시 할계획 이라고설명했다. 이처럼삼성전자와 LG 필립스 LCD 가 LED BLU 를활 용한 TV 용 LCD 패널출시를서두르고있는가운데그간상용화의걸림돌로 작용했던 LED 의높은가격과높은소비전력, 발열문제등이점차개선되고 가격또한경쟁을통해빠르게하락할전망이어서향후 LED BLU 채택은빠른 속도로확산될것으로예상된다. 디지털산업 2006 년 04 월 24 일 글싣는순서 I. 최근연구동향 1. GaN based optoelectronics 2. Si Quantum dot based optoelectronics 3. ZnO based optoelectronics II. 연구논문소개 - 제목 : 1. GaInN light-emitting diode with conductive omnidirectional reflector having a low-refractive-index indium-tin oxide layer 2. ZnO p-n junction light-emitting diodes fabricated on sapphire substrates
I. 최근연구동향소개 1. GaN based optoelectronics Lumileds compact Luxeon LED targets flashlights Ref) COMPOUNDSEMI 15 Feb 2006 Lumileds Lighting has released the Luxeon Portable PWT1, which it says is the market's smallest power LED designed for flashlights and other portable lighting applications. According to the company, the new emitter generates 26 lumens at 350mA from a package size of 2.0 x 1.6 x 0.7mm, providing market-leading light output for its size along with a 2,000-hour life and uniform white light produced by Lumileds' patented conformal coating process. The Luxeon Portable PWT1 is roughly 75% smaller than other LEDs with similar light output and delivers about 4.5 times the amount of light (lumens) per square millimeter, says Lumileds. This enables manufacturers to build flashlights and other portable lighting products with smaller optics, smaller form factors and less weight than ever before. Luxeon Portable PWT1 offers the moisture sensitivity rating--jedec level 1--allowing for unlimited factory floor life. This eliminates the need for dry storage or baking of the package after exposure to air, says the company. The surface-mount package is said to simplify manufacturing and offer the toughest electrostatic discharge (ESD) protection in the industry with an 8kV ESD protection chip. Lumileds' exclusive die coating technology is claimed to ensure uniform coloration in the beam pattern, eliminating commercially unacceptable color irregularities that occur with white LEDs from other vendors because of a lack of uniformity in phosphor coverage of the die. Lumileds utilizes special tools and procedures to distribute the phosphor at a regulated and consistent thickness over the entire Luxeon chip. The new emitter, which is lead-free and RoHS compliant, expands Lumileds' family of portable LEDs, which also includes the larger Luxeon V Portable with a 500-hour life and a typical flux of 120 lumens at 700 ma. The datasheet (DS51) and "Portable Lighting Designer's Guide are available now along with pricing and availability from Lumileds Future Electronics at www.lumiledsfuture.com or 1-888-LUXEON2.
2. Si Quantum dot based optoelectronics Enhanced Radiative Emission Rate and Quantum Efficiency in Coupled Silicon Nanocrystal-Nanostructured Gold Emitters Julie S. Biteen,* Domenico Pacifici, Nathan S. Lewis, and Harry A. Atwater California Institute of Technology, 1200 East California BouleVard, Pasadena, California 91125 Received June 25, 2005; Revised Manuscript Received July 28, 2005, Nanoletters 5, pp.1768-1773 We report local-field-enhanced light emission from silicon nanocrystals close to a film of nanoporous gold. We resolve photoluminescence as the gold-si nanocrystal separation distance is varied between 0 and 20 nm and observe a fourfold luminescence intensity enhancement concomitant with increases in the coupled silicon nanocrystal/nanoporous gold absorbance cross section and radiative decay rate. A detailed analysis of the luminescence data indicated a local-field-enhanced quantum efficiency of 58% for the Si nanocrystals coupled to the nanoporous gold layer. 3. ZnO based optoelectronics Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays SCIENCE VOL 312 14 APRIL 2006 We have converted nanoscale mechanical energy into electrical energy by means of piezoelectric zinc oxide nanowire (NW) arrays. The aligned NWs are deflected with a conductive atomic force microscope tip in contact mode. The coupling of piezoelectric and semiconducting properties in zinc oxide creates a strain field and charge separation across the NW as a result of its bending. The rectifying characteristic of the Schottky barrier formed between the metal tip and the NW leads to electrical current generation. The efficiency of the NW-based piezoelectric power generator is estimated to be 17 to 30%. This approach has the potential of converting mechanical, vibrational, and/or hydraulic energy into electricity for powering nanodevices.
II. 연구논문소개 1. GaInN light-emitting diode with conductive omnidirectional reflector having a low-refractive-index indium-tin oxide layer
Jong Kyu Kim, Thomas Gessmann, and E. Fred Schubert Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 J.-Q. Xi and Hong Luo Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 Jaehee Cho, Cheolsoo Sone, and Yongjo Park Photonics Program Team, Samsung Advanced Institute of Technology, Suwon 440-600, South Korea (Received 31 August 2005; accepted 28 November 2005; published online 3 January 2006) Appl. Phys. Lett. 88, 013501 (2006) Enhancement of light extraction in a GaInN light-emitting diode (LED) employing a conductive omnidirectional reflector (ODR) consisting of GaN, an indium-tin oxide (ITO) nanorod low-refractive-index layer, and an Ag layer is presented. An array of ITO nanorods is deposited on p-type GaN by oblique-angle electron-beam deposition. The refractive index of the nanorod ITO layer is 1.34 at 461 nm, significantly lower than that of dense ITO layer, which is n=2.06. The GaInN LEDs with GaN/low-n ITO/Ag ODR show a lower forward voltage and a 31.6% higher light-extraction efficiency than LEDs with Ag reflector. This is attributed to enhanced reflectivity of the ODR that employs the low-n ITO layer 2. ZnO p-n junction light-emitting diodes fabricated on sapphire substrates S. J. Jiao, Z. Z. Zhang, Y. M. Lu, D. Z. Shen, B. Yao, J. Y. Zhang, B. H. Li, D. X. Zhao, X. W. Fan, and Z. K. Tang Appl. Phys. Lett. 88, 031911 (2006) A ZnO p-njunction light-emitting diode (LED) was fabricated on a-plane Al 2 O 3 substrate by plasma-assisted molecular-beam epitaxy. NO plasma activated by a radio frequency atomic source was used to grow the p-type ZnO layer of the LED. The current-voltage measurements at low temperatures showed a typical diode characteristic with a threshold voltage of about 4.0V under forward bias. With increasing temperature, the rectification characteristic was degraded gradually, and faded away at room temperature. Electroluminescence band of the ZnO p-n junction LED was located at the blue-violet region and was weakened significantly with increase of temperature. This thermal quenching of the electroluminescence was attributed to the degradation of the diode characteristic with temperature.