共查询到20条相似文献,搜索用时 31 毫秒
1.
S.J. Chang L.W. Wu Y.K. Su Y.P. Hsu W.C. Lai J.M. Tsai J.K. Sheu C.T. Lee 《Photonics Technology Letters, IEEE》2004,16(6):1447-1449
GaN-based light-emitting diodes (LEDs) with various p-cap layers were prepared. It was found that surface morphologies of the LEDs with 800/spl deg/C grown cap layers were rough due to the low lateral growth rate of GaN. It was also found that 20-mA forward voltage of the LED with 800/spl deg/C grown p-AlInGaN-GaN double-cap layer was only 3.05 V. Furthermore, it was found that we could achieve a high output power and a long lifetime by using the 800/spl deg/C grown p-AlInGaN-GaN double-cap layer. 相似文献
2.
Wu L.W. Chang S.J. Wen T.C. Su Y.K. Chen J.F. Lai W.C. Kuo C.H. Chen C.H. Sheu J.K. 《Quantum Electronics, IEEE Journal of》2002,38(5):446-450
A detailed study on the effects of Si-doping in the GaN barrier layers of InGaN-GaN multiquantum well (MQW) light-emitting diodes (LEDs) has been performed. Compared with unintentionally doped samples, X-ray diffraction results indicate that Si-doping in barrier layers can improve the crystal and interfacial qualities of the InGaN-GaN MQW LEDs. It was also found that the forward voltage is 3.5 and 4.52 V, the 20-mA luminous intensity is 36.1 and 25.1 mcd for LEDs with a Si-doped barrier and an unintentionally doped barrier, respectively. These results suggests that one can significantly improve the performance of InGaN-GaN MQW LEDs by introducing Si doping in the GaN barrier layers 相似文献
3.
Light-output enhancement in a nitride-based light-emitting diode with 22/spl deg/ undercut sidewalls
Chih-Chiang Kao Hao-Chung Kuo Hung-Wen Huang Jung-Tang Chu Yu-Chun Peng Y.-L. Hsieh C.Y. Luo Shing-Chung Wang Chang-Chin Yu Chia-Feng Lin 《Photonics Technology Letters, IEEE》2005,17(1):19-21
We successfully fabricated nitride-based light-emitting diodes (LEDs) with /spl sim/22/spl deg/ undercut sidewalls. The /spl sim/22/spl deg/ etching undercut sidewalls were achieved by controllable inductively coupled plasma reactive ion etching. With a 20-mA current injection, the output powers of the LED with /spl sim/22/spl deg/ undercut sidewalls and standard LED were 5.1 and 3 mW, respectively-a factor of 1.7 times enhancement. It was found that such undercut sidewalls could enhance the probability of escaping the photons outside from the LED in the near horizontal and in-plane directions. This simple and controllable method is beneficial to fabricate brighter LEDs. 相似文献
4.
Wei S.C. Su Y.K. Chang S.J. Shi-Ming Chen Wen-Liang Li 《Electron Devices, IEEE Transactions on》2005,52(6):1104-1109
Nitride-based light emitting diodes (LEDs) separately prepared with a conventional single low-temperature (LT) GaN nucleation layer and multiple GaN-SiN nucleation layers were both prepared. It was found that we could reduce defect density and thus improve crystal quality of the GaN-based LEDs by using multiple GaN-SiN nucleation layers. With a 20-V applied reverse bias, it was found that the reverse leakage currents measured from the LED with a single LT GaN nucleation layer and the one with 10-pair GaN-SiN nucleation layers were 1.5/spl times/10/sup -4/ and 2.5/spl times/10/sup -6/ A, respectively. It was also determined that we could use the multiple GaN-SiN nucleation layers to enhance the output intensity of near ultraviolet (UV) LEDs and to improve the reliability of nitride-based LEDs. 相似文献
5.
T. C. Wen S. J. Chang Y. K. Su L. W. Wu C. H. Kuo W. C. Lai J. K. Sheu T. Y. Tsai 《Journal of Electronic Materials》2003,32(5):419-422
High-quality InGaN/GaN multiple-quantum well (MQW) light-emitting diode (LED) structures were prepared by a temperature-ramping
method during metal-organic chemical-vapor deposition (MOCVD) growth. Two photoluminescence (PL) peaks, one originating from
well-sensitive emission and one originating from an InGaN quasi-wetting layer on the GaN-barrier surface, were observed at
room temperature (RT). The observation of high-order double-crystal x-ray diffraction (DCXRD) satellite peaks indicates that
the interfaces between InGaN-well layers and GaN-barrier layers were not degraded as we increased the growth temperature of
the GaN-barrier layers. With a 20-mA and 160-mA current injection, it was found that the output power could reach 2.2 mW and
8.9 mW, respectively. Furthermore, it was found that the reliability of the fabricated green LEDs prepared by temperature
ramping was also reasonably good. 相似文献
6.
S.J. Chang C.S. Chang Y.K. Su R.W. Chuang W.C. Lai C.H. Kuo Y.P. Hsu Y.C. Lin S.C. Shei H.M. Lo J.C. Ke J.K. Sheu 《Photonics Technology Letters, IEEE》2004,16(4):1002-1004
The indium-tin-oxide [ITO(80 nm)] and Ni(5 nm)-Au(10 nm) films were separately deposited on glass substrates, p-GaN layers, n/sup +/-InGaN-GaN short-period-superlattice (SPS) structures, and nitride-based light-emitting diodes (LEDs). It was found that ITO on n/sup +/-SPS structure could provide us an extremely high transparency (i.e., 93.2% at 465 nm) and also a reasonably small specific contact resistance of 1.6/spl times/10/sup -3//spl Omega//spl middot/cm/sup 2/. Although the forward voltage which corresponds to 20-mA operating current for LED with ITO on n/sup +/-SPS upper contact was slightly higher than that of the LED with Ni-Au on n/sup +/-SPS upper contact, a 30% higher output intensity could still be achieved by using ITO on n/sup +/-SPS upper contact. Moreover, the output power of packaged LED with ITO was about twice as large as that of the other conventional Ni-Au LEDs. 相似文献
7.
Chen W.S. Shei S.C. Chang S.J. Su Y.K. Lai W.C. Kuo C.H. Lin Y.C. Chang C.S. Ko T.K. Hsu Y.P. Shen C.F. 《Electron Devices, IEEE Transactions on》2006,53(1):32-37
Nitride-based flip-chip (FC) light-emitting diodes (LEDs) emitting at 465 nm with Ni transparent ohmic contact layers and Ag reflective mirrors were fabricated. With an incident light wavelength of 465 nm, it was found that transmittance of normalized 300/spl deg/C rapid thermal annealed (RTA) Ni(2.5 nm) was 93% while normalized reflectance of 300/spl deg/C RTA Ni(2.5 nm)/Ag(200 nm) was 92%. It was also found that 300/spl deg/C RTA Ni(2.5 nm) formed good ohmic contact on n/sup +/ short-period-superlattice structure with specific contact resistance of 7.8/spl times/10/sup -4/ /spl Omega//spl middot/cm/sup 2/. With 20-mA current injection, it was found that forward voltage and output power were 3.15 V and 16.2 mW for FC LED with 300/spl deg/C RTA Ni(2.5 nm)/Ag(200 nm). Furthermore, it was found that reliabilities of FC LEDs were good. 相似文献
8.
Su Y.K. Chang S.J. Wei S.C. Chuang R.W. Chen S.M. Li W.L. 《Electron Device Letters, IEEE》2005,26(12):891-893
Nitride-based light-emitting diodes (LEDs) with n/sup -/-GaN current spreading layers were proposed and fabricated. With a 0.1-/spl mu/m-thick n/sup -/-GaN current spreading layer, it was found that the output power could be enhanced by 35% without increasing the operation voltage of the LEDs at 20 mA. In addition, implementing the n/sup -/-GaN current spreading layer also significantly improved the electrostatic discharge characteristics of nitride-based LEDs. 相似文献
9.
Chang C.S. Chang S.J. Su Y.K. Kuo C.H. Lai W.C. Lin Y.C. Hsu Y.P. Shei S.C. Tsai J.M. Lo H.M. Ke J.C. Sheu J.K. 《Electron Devices, IEEE Transactions on》2003,50(11):2208-2212
Indium tin oxide (ITO) (260 nm) and Ni (5 nm)/Au (10 nm) films were deposited onto glass substrates, p-GaN layers, n/sup +/-InGaN/GaN short-period-superlattice (SPS), n/sup ++/-SPS and nitride-based green light-emitting diodes (LEDs). It was found that ITO could provide us an extremely high transparency (i.e., 95% at 520 nm). It was also found that the 1.03/spl times/10/sup -3/ /spl Omega/cm/sup 2/ specific contact resistance of ITO on n/sup ++/-SPS was reasonably small. Although the forward voltage of the LED with ITO on n/sup ++/-SPS upper contacts was slightly higher than that of the LED with Ni/Au on n/sup ++/-SPS upper contacts, the 20 mA output power and external quantum efficiency of the former could reach 4.98 mW and 8.2%, respectively, which were much larger than the values observed from the latter. The reliability of ITO on n/sup ++/-SPS upper contacts was also found to be reasonably good. 相似文献
10.
Chang S.J. Chen W.S. Shei S.C. Ko T.K. Shen C.F. Hsu Y.P. Chang C.S. Tsai J.M. Lai W.C. Lin A.J. 《Advanced Packaging, IEEE Transactions on》2007,30(4):752-757
The properties of indium-tin-oxide (ITO)/Ni films as transparent ohmic contacts of nitride-based flip chip (FC) light emitting diodes (LEDs) were studied. It was found that 300degC rapid thermal annealed (RTA) ITO(15 nm)/Ni(1 nm) could provide good electrical and optical properties for FC LED applications. It was also found that 20-mA operation voltage and output power of the 465-nm FC LEDs with ITO/Ni/Ag reflective mirror were 3.16 V and 21 mW, respectively. Furthermore, it was found that output intensity of the proposed LED only decayed by 5% after 1200 h under 30-mA current injection at room temperature. 相似文献
11.
Low resistance and reflective Mg-doped indium oxide-Ag ohmic contacts for flip-chip light-emitting diodes 总被引:1,自引:0,他引:1
J.-O. Song Dong-Seok Leem J.S. Kwak O.H. Nam Y. Park Tae-Yeon Seong 《Photonics Technology Letters, IEEE》2004,16(6):1450-1452
We have investigated an Mg-doped In/sub x/O/sub y/(MIO)-Ag scheme for the formation of high-quality ohmic contacts to p-type GaN for flip-chip light-emitting diodes (LEDs). The as-deposited sample shows nonlinear current-voltage (I--V) characteristics. However, annealing the contacts at temperatures of 330/spl deg/C-530/spl deg/C for 1 min in air ambient results in linear I--V behaviors, producing specific contact resistances of 10/sup -4/--10/sup -5/ /spl Omega//spl middot/cm/sup 2/. In addition, blue LEDs fabricated with the MIO-Ag contact layers give forward-bias voltages of 3.13-3.15 V at an injection current of 20 mA. It is further shown that LEDs made with the MIO-Ag contact layers give higher output power compared with that with the Ag contact layer. This result strongly indicates that the MIO-Ag can be a promising scheme for the realization of high brightness LEDs for solid-state lighting application. 相似文献
12.
Hsu S.-C. Lee C.-Y. Hwang J.-M. Su J.-Y. Wuu D.-S. Horng R.-H. 《Photonics Technology Letters, IEEE》2006,18(23):2472-2474
We have demonstrated enhanced output power from roughened GaN-based light-emitting diodes (LEDs) by using electrodeless photoelectrochemical etching with a chopped source (ELPEC-CS etching). It was found that the 20-mA output power of the ELPEC-CS treated LED (with roughened surfaces on the top p-type and bottom n-type GaN surface as well as the mesa sidewall) was 1.41 and 2.57 times as high as those LEDs with a roughened p-type GaN surface and a conventional surface, respectively. The light output pattern of the ELPEC-CS treated LED was five times greater than the conventional LED at 0deg which was caused by the roughened GaN surface that improved the light extraction efficiency of the LED 相似文献
13.
Ru-Chin Tu Chun-Ju Tun Shyi-Ming Pan Hai-Ping Liu Ching-En Tsai J.K. Sheu Chang-Cheng Chuo Te-Chung Wang Gou-Chung Chi In-Gann Chen 《Photonics Technology Letters, IEEE》2003,15(8):1050-1052
The 410-nm near-ultraviolet (near-UV) InGaN-GaN multiple quantum-wells light-emitting diodes (LEDs) with low-pressure-grown (200 mbar) and high-pressure-grown (400 mbar) Si-doped GaN underlying layers were grown on c-face sapphire substrates by metal-organic vapor phase epitaxy. Increasing the growth pressure during the initial growth of the underlying n-type GaN epilayers of the near-UV InGaN-GaN LEDs was found to reduce the amount of threading dislocations that originated from the GaN-sapphire interfaces. The electroluminescence intensity of LEDs with underlying GaN layers grown at a higher pressure was nearly five times larger than that of LED with layers grown at lower pressure. Additionally, two-order reduction of leakage current was also induced for the LEDs grown at a higher pressure. 相似文献
14.
In this letter, a GaN/sapphire light-emitting diode (LED) structure was designed with improved electrostatic discharge (ESD) performance through the use of a shunt GaN ESD diode connected in inverse-parallel to the GaN LED. Thus, electrostatic charge can be discharged from the GaN LED through the shunt diode. We found that the ESD withstanding capability of GaN/sapphire LEDs incorporating this ESD-protection feature could be increased from several hundreds up to 3500 V in the human body model. Furthermore, flip-chip (FC) technology was also used to produce ESD-protected LEDs to further improve light output power and reliability. At a 20-mA current injection, the output power of the FC LEDs showed an improvement of around 60%. After a 1200-h aging test, the luminous intensities of the FC LEDs featuring an internal ESD-protection diode decreased by 4%. This decay percentage was far less than those of non-FC LEDs 相似文献
15.
《Photonics Technology Letters, IEEE》2009,21(22):1659-1661
16.
Nitride-based cascade near white light-emitting diodes 总被引:5,自引:0,他引:5
Chen C.H. Chang S.J. Su Y.K. Sheu J.K. Chen J.F. Kuo C.H. Lin Y.C. 《Photonics Technology Letters, IEEE》2002,14(7):908-910
An InGaN-GaN blue light-emitting diode (LED) structure and an InGaN-GaN green LED structure were grown sequentially onto the same sapphire substrate so as to achieve a nitride-based near white LED. In order to avoid thyristor effect, we choose a large 2.1×2.1 mm2 LED chip size, which was six times larger than that of the normal LED. It was found that we could observe a near white light emission with Commission International de l'Eclairage color coordinates x=0.2 and y=0.3, when the injection current was lower than 200 mA. It was also found that the output power, luminous efficiency and color temperature of such a cascade near white LED were 4.2 mW, 81 l m/W, and 9000 K, respectively 相似文献
17.
InGaN-AlInGaN multiquantum-well LEDs 总被引:2,自引:0,他引:2
Wei-Chih Lai Shoou-Jinn Chang Yokoyam M. Jinn-Kong Sheu Chen J.F. 《Photonics Technology Letters, IEEE》2001,13(6):559-561
InGaN-GaN and InGaN-AlInGaN multiquantum-well (MQW) light-emitting diodes (LEDs) were both fabricated and their optical properties were evaluated by photoluminescence (PL) as well as electroluminescence (EL). We found that the PL peak position of the InGaN-AlInGaN MQW occurs at a much lower wavelength than that of the InGaN-GaN MQW. The PL intensity of the InGaN-AlInGaN MQW was also found to be larger. The EL intensity of the InGaN-AlInGaN MQW LED was also found to be larger than that of the InGaN-GaN MQW LED under the same amount of injection current. Furthermore, it was found that EL spectrum of the InGaN-AlInGaN MQW LED is less sensitive to the injection current. These observations all suggest that we can improve the properties of nitride-based LEDs by using AlInGaN as the barrier layer 相似文献
18.
An-Ting Cheng Yan-Kuin Su Wei-Chi Lai 《Photonics Technology Letters, IEEE》2008,20(12):970-972
We report the growth of AlInN nearly lattice-matched to GaN using metal-organic vapor phase epitaxy. The full-width at half-maximum of the AlInN peak measured by double crystal X-ray diffraction was 219.8 arcsec for the indium content of 20.8%. The effects of AlInN cladding layers on InGaN-GaN multiple-quantum-well light-emitting diodes (LEDs) were also investigated. From the room-temperature photoluminescence spectra, the shorter emission wavelength and the higher intensity were observed after employing AlInN cladding layers. Compared to the conventional LED, the light output intensity of the LED with AlInN cladding layers was increased due to the enhanced carrier confinement. Besides, we found the light output intensity could be saturated at higher injection current. Although the electrical property of the LED with AlInN cladding layers was slightly degraded, the experimental results in this study could explain the potential applicability of AlInN to the fabrication of cladding layers. 相似文献
19.
Shyi-Ming Pan Ru-Chin Tu Yu-Mei Fan Ruey-Chyn Yeh Jung-Tsung Hsu 《Photonics Technology Letters, IEEE》2003,15(5):646-648
This study develops a highly transparent nickel-oxide (NiO/sub x/)-indium-tin-oxide (ITO) transparent Ohmic contact with excellent current spreading for p-GaN to increase the optical output power of nitride-based light-emitting diodes (LEDs). The NiO/sub x/-ITO transparent Ohmic contact layer was prepared by electron beam in-situ evaporation without postdeposition annealing. Notably, the transmittance of the NiO/sub x/-ITO exceeds 90% throughout the visible region of the spectrum and approaches 98% at 470 nm. Moreover, GaN LED chips with dimensions of 300 /spl times/ 300 /spl mu/m fabricated with the NiO/sub x/-ITO transparent Ohmic contact were developed and produced a low forward voltage of 3.4 V under a nominal forward current of 20 mA and a high optical output power of 6.6 mW. The experimental results indicate that NiO/sub x/-ITO bilayer Ohmic contact with excellent current spreading and high transparency is suitable for fabricating high-brightness GaN-based light-emitting devices. 相似文献
20.
C. S. Kim H. K. Cho M. K. Yoo H. S. Cheong C. -H. Hong H. K. Cho 《Journal of Electronic Materials》2004,33(5):445-449
Correlation between material properties of bulk p-GaN layers grown on undoped GaN and device performance of InGaN/GaN blue
light-emitting diodes (LEDs) as a function of p-GaN growth temperature were investigated. The p-GaN layers of both structures
grown by metal-organic chemical-vapor deposition were heavily doped with Mg. As the growth temperature of the bulk p-GaN layer
increased up to 1,080°C, NA-ND increased. However, above 1,110°C, NA-ND sharply decreased, while the fluctuation of Mg concentration ([Mg]) increased. At this time, a peculiar surface, which originated
from inversion domain boundaries (IDBs), was clearly observed in the bulk p-GaN layer. The IDBs were not found in all LEDs
because the p-GaN contact layer was relatively thin. The change in photoluminescence emission from the ultraviolet band to
blue band is found to be associated with the fluctuation of [Mg] and IDBs in bulk p-GaN layers. The LED operating voltage
and reverse voltage improved gradually up to the p-GaN contact-layer growth temperature of 1,080°C. However, the high growth
temperature of 1,110°C, which could favor the formation of IDBs in the bulk p-GaN layer, yielded poorer reverse voltage and
saturated output power of the LEDs. 相似文献