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1.
Nano-hole patterned sapphire substrates (NHPSSs) were successfully prepared using a low-cost and high-efficiency approach, which is the laser interference lithography (LIL) combined with reactive ion etching (RIE) and inductively coupled plasma (ICP) techniques. Gallium nitride (GaN)-based light emitting diode (LED) structure was grown on NHPSS by metal organic chemical vapor deposition (MOCVD). Photoluminescence (PL) measurement was conducted to compare the luminescence efficiency of the GaN-based LED structure grown on NHPSS (NHPSS-LED) and that on unpatterned sapphire substrates (UPSS-LED). Electroluminescence (EL) measurement shows that the output power of NHPSS-LED is 2.3 times as high as that of UPSS-LED with an injection current of 150 mA. Both PL and EL results imply that NHPSS has an advantage in improving the crystalline quality of GaN epilayer and light extraction efficiency of LEDs at the same time. 相似文献
2.
Chih-Hung Yen Yi-Jung Liu Tzu-Pin Chen Li-Yang Chen Tsung-Han Tsai Wen-Chau Liu 《Photonics Technology Letters, IEEE》2009,21(10):609-611
An AlGaInP-based multiquantum-well (MQW) light-emitting diode (LED) with an n-type modulation-doped (MD) structure, grown by metal-organic vapor-phase epitaxy, is fabricated and studied. Experimental results indicate that a lower turn-on voltage and dynamic resistance, higher output power, and smaller wavelength shift, as compared to a conventional undoped-MQW LED, are obtained. The studied n-type MD-MQW LED also exhibits a higher external quantum efficiency of 7.2% and a larger maximum light output power. The junction temperature of the studied MD-MQW LED also shows a 12 degC reduction, at 200 mA, as compared to a conventional one. These positive results are mainly attributed to the presence of a higher electron concentration in the MD-MQW active region. 相似文献
3.
High light-extraction (external quantum efficiency ~40%) 465-nm GaN-based vertical light-emitting diodes (LEDs) employing double diffuse surfaces were fabricated. This novel LED structure includes one top transmitted diffuse surface and another diffuse omnidirectional reflector (ODR) on the bottom of a LED chip. The diffusive ODR consists of a roughened p-type GaN layer, an indium-tin-oxide (ITO) low refractive index layer, and an Al layer. The surface of the p-type GaN-layer was naturally roughened while decreasing the growth temperature to 800 degC. After flip-bonding onto a Si substrate by AuSn eutectic metal and laser lift-off processes to remove the sapphire substrate, an anisotropic etching by dilute potassium hydroxide (KOH) was employed on the N-face n-GaN layer to obtain transmitted diffuse surfaces with hexagonal-cone morphology. The double diffused surfaces LEDs show an enhancement of 56% and 236% in light output power compared to single side diffused surface and conventional LEDs, respectively. The devices also show a low leakage current in the order of magnitude of 10 -8 A at -5 V and a calculated external quantum efficiency of about 40%. The high scattering efficiency of double diffused surfaces could be responsible for the enhancement in the device light output power 相似文献
4.
《Photonics Technology Letters, IEEE》2009,21(12):760-762
5.
《Photonics Technology Letters, IEEE》2009,21(5):331-333
6.
Lee Y.J. Kuo H.C. Wang S.C. Hsu T.C. Hsieh M.H. Jou M.J. Lee B.J. 《Photonics Technology Letters, IEEE》2005,17(11):2289-2291
An n-side-up AlGaInP-based light-emitting diode (LED) with a triangle-like surface morphology was fabricated using the adhesive layer bonding technique, followed by wet etching to roughen the surface. The light output power of the roughened-surface LED was 1.6 times higher than that of a flat-surface LED at an injection current of 20 mA, i.e., a significant improvement attributed to the ability of the roughened surface to not only reduce the internal reflection between the rear mirror system and the semiconductor-air interface, but also to effectively scatter the light outside the LED device. 相似文献
7.
研究一种表面再构的具有全方位反光镜(ODR)结构的倒装AlGaInP半导体发光二极管(LED)。通过湿法腐蚀方法再构N-AlGaInP盖层表面,形成类金字塔的表面结构,使不同角度入射的光有更多的机会出射。比较了表面再构LED与常规LED的电、光学特性,在注入电流为20 mA时,经过表面再构LED的轴向光强和输出光功率是常规LED的1.5倍,表面再构后大大提高了LED的外量子效率,减少了LED内部热量的积累,提高了LED芯片的可靠性。 相似文献
8.
Chia-Feng Lin Kuei-Ting Chen Chun-Min Lin Chung-Chieh Yang 《Electron Device Letters, IEEE》2009,30(10):1057-1059
InGaN-based light-emitting diodes (LEDs) with nanoporous microhole array (NMA) structures were fabricated through photoelectrochemical wet oxidation and oxide-removing processes. The average size of the nanoporous structure at the microhole regions was measured at 60-80 nm. Forward voltages were measured at 3.47 and 3.68 V for a standard LED (ST-LED) and an NMA-LED, respectively, the latter caused by the higher contact resistance at the nanoporous GaN:Mg surface. The light output power of the NMA-LED had a 40.5% enhancement compared with the ST-LED on nonencapsulated LEDs in chip form. The higher light scattering process occurred at the NMA structure on the GaN:Mg surface and at the ringlike patterns on the GaN:Si structure. The results were a higher light extraction efficiency and a larger divergent angle in the NMA-LED. 相似文献
9.
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
10.
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
11.
Y.J. Lee J.M. Hwang T.C. Hsu M.H. Hsieh M.J. Jou B.J. Lee T.C. Lu H.C. Kuo S.C. Wang 《Photonics Technology Letters, IEEE》2006,18(10):1152-1154
GaN-based light-emitting diodes (LEDs) with emitting wavelength of 450 nm were grown on patterned sapphire substrates (PSSs) fabricated by chemical wet etching. The crystallography-etched facet was {1-102} R-plane with a 57/spl deg/ against {0001} C-axis and had superior capability for enhancing light extraction efficiency. The light output power of the PSS LED was 1.15 times higher than that of the conventional LED at an injection current of 20 mA. The output power and external quantum efficiency were estimated to be 9 mW and 16.4%, respectively. The improvement was attributed not only to geometrical shapes of {1-102} crystallography-etched facets that efficiently scatter the guided light to find escape cones, but also to dislocation density reduction by adopting the PSS growth scheme. 相似文献
12.
Ming-Kwei Lee Chen-Lin Ho Po-Chun Chen 《Photonics Technology Letters, IEEE》2008,20(4):252-254
We investigate the light extraction efficiency of a GaN light-emitting diode (LED) by using liquid-phase-deposited ZnO rods at near-room temperature. Zinc nitrate and hexamethylenetetramine were used as the deposition precursors. Compared with the conventional GaN LED, the optical power output of the GaN LED with crystalline ZnO rods on its surface has about 1.6 times enhancement. 相似文献
13.
Chung-Chieh Yang Chia-Feng Lin Jen-Hao Chiang Hsun-Chih Liu Chun-Min Lin Feng-Hsu Fan Chung-Ying Chang 《Journal of Electronic Materials》2009,38(1):145-152
InGaN-based light-emitting diodes (LEDs) were fabricated to have a higher light extraction through the photoelectrochemical
(PEC) mesa shaping process. After the PEC selective wet oxidation and wet etching processes, stable and controllable crystallographic
etching planes were formed as p-type GaN {} planes and n-type GaN {} planes included at an angle of 27 deg. The ever-present cone-shaped structure of a PEC-treated LED has a larger light scattering
area and higher light extraction cones on the mesa sidewall, as analyzed by microphotoluminescence and light output power
measurement. This cone-shaped-sidewall LED has a higher light output power and a larger divergence angle compared with a conventional
LED measured in an LED chip form. 相似文献
14.
We report on the high-performance of InGaN multiple-quantum well light-emitting diodes (LEDs) on Si (111) substrates using metal-organic chemical vapor deposition. A high-temperature thin AlN layer and AlN-GaN multilayers have been used for the growth of high-quality GaN-based LED structure on Si substrate. It is found that the operating voltage of the LED at 20 mA is reduced to as low as 3.8-4.1 V due to the formation of tunnel junction between the n-AlGaN layer and the n-Si substrate when the high-temperature AlN layer is reduced to 3 nm. Because Si has a better thermal conductivity than sapphire, the optical output power of the LED on Si saturates at a higher injected current density. When the injected current density is higher than 120 A/cm/sup 2/, the output power of the LED on Si is higher than that of LED on sapphire. The LED also exhibited the good reliability and the uniform emission from a large size wafer. Cross-sectional transmission electron microscopy observation indicated that the active layer of these LEDs consists of the dislocation-free pyramid-shaped (quantum-dot-like) structure. 相似文献
15.
GaN-based LEDs with photonic crystal (PhC) patterns on an n- and a p-GaN layer by nano-imprint lithography (NIL) are fabricated and investigated. At a driving current of 20 mA on Transistor Outline (TO)-can package, the light output power of the GaN-based LED with PhC patterns on an n- and a p-GaN layer is enhanced by a factor of 1.30, and the wall-plug efficiency is increased by 24%. In addition, the higher output power of the LED with PhC patterns on the n- and p-GaN layer is due to better crystal quality on n-GaN and higher scattering effect on p-GaN surface using PhC pattern structure. 相似文献
16.
Enhanced output power of near-ultraviolet InGaN-GaN LEDs grown on patterned sapphire substrates 总被引:1,自引:0,他引:1
D.S. Wuu W.K. Wang W.C. Shih R.H. Horng C.E. Lee W.Y. Lin J.S. Fang 《Photonics Technology Letters, IEEE》2005,17(2):288-290
Near-ultraviolet nitride-based light-emitting diodes (LEDs) with peak emission wavelengths around 410 nm were fabricated onto c-face patterned sapphire substrates (PSS). It was found that the electroluminescence intensity of the PSS LED shown 63% larger than that of the conventional LED. For a typical lamp-form PSS LED operating at a forward current of 20 mA, the output power and external quantum efficiency were estimated to be 10.4 mW and 14.1%, respectively. The improvement in the light intensity could be attributed to the decrease of threading dislocations and the increase of light extraction efficiency in the horizontal direction using a PSS. 相似文献
17.
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
18.
19.
Ming-Kwei Lee Chen-Lin Ho Cho-Han Fan 《Photonics Technology Letters, IEEE》2008,20(15):1293-1295
Silicon oxide (SiO2) hemispherical microlens with the density of 8.2 times 108 cm-2 has been formed on a sapphire substrate of gallium nitride (GaN) light-emitting diode (LED) by liquid phase deposition to enhance the light extraction efficiency. For flip-chip LED, the SiO2 microlens exhibits 1.25 times enhancement of optical output power. In comparison of the conventional LED, there is 61% enhancement for flip-chip LED with a SiO2 microlens. 相似文献
20.
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