共查询到20条相似文献,搜索用时 31 毫秒
1.
采用金属有机物化学气相沉积(MOCVD)技术生长了具有高In组分InGaN阱层的InGaN/GaN多量子阱(MQW)结构,高分辨X射线衍射(HRXRD)ω-2θ扫描拟合得到阱层In含量28%。比较大的表面粗糙度表明有很大的位错密度。室温下光致荧光(PL)研究发现该量子阱发射可见的红橙光,峰位波长在610 nm附近。变温PL(15~300 K)进一步揭示量子阱在低温下有两个发光机制,对应的发射峰波长分别为538 nm和610 nm。由于In分凝和载流子的局域化导致的载流子动力改变,使得量子阱PL发光峰值随温度增加呈明显的"S"变化趋势。 相似文献
2.
Blue and green dual wavelength InGaN/GaN multi-quantum well (MQW) light-emitting diode (LED) has wide applications in full color display, monolithic white LED and solid state lighting, etc. Blue and green dual wavelength LEDs, which consist of InGaN strain-reduction layer, green InGaN/GaN MQW and blue InGaN/ GaN MQW, were grown by metal-organic chemical vapor deposition (MOCVD), and the luminescence properties of dual wavelength LEDs with different well arrangements were studied by photoluminescence and electrolumines-cence. The experimental results indicated that well position played an important role on the luminescence evolvement from photoluminescence to electroluminescence. 相似文献
3.
为了减弱InGaN/GaN量子阱内的压电极化场,在蓝紫光InGaN/GaN多量子阱激光器结构中采用了预应变InGaN插入层,通过变温电致发光和高分辨X射线衍射测量研究了预应变插入层对量子阱晶体质量和发光特性的影响。实验结果显示,常温下有预应变层的量子阱电致发光谱积分强度显著提高。模拟计算进一步表明,预应变层对量子阱内压电极化场有调制效果,有利于量子阱中的应力弛豫,可以有效减弱量子限制斯塔克效应,有助于提高量子阱的发光效率。 相似文献
4.
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
5.
Lee‐Woon Jang Dae‐Woo Jeon Myoung Kim Ju‐Won Jeon Alexander Y. Polyakov Jin‐Woo Ju Seung‐Jae Lee Jong‐Hyeob Baek Jin‐Kyu Yang In‐Hwan Lee 《Advanced functional materials》2012,22(13):2728-2734
Localized surface plasmon (LSP) effects due to Ag and Ag/SiO2 nanoparticles (NPs) deposited on GaN/InGaN multiquantum well (MQW) light‐emitting diode (LED) structures are studied. The colloidal NPs are synthesized by a sol‐gel method and drop‐cased on the LED structures. The surface density of NPs its controlled by the concentration of the NP solution. Theoretical modeling is performed for the emission spectrum and the electric field distribution of LSP resonance for Ag/SiO2 NPs. Enhanced photoluminescence (PL) efficiency is observed in the LED structures and the amount of PL enhancement increases with increasing the surface density of Ag and Ag/SiO2 NPs. These effects are attributed to resonance coupling between the MQW and LSP in the NPs. It is also shown that the PL enhancement attainable with Ag NPs and Ag/SiO2 NPs is comparable, but the latter displays a much higher stability with respect to long‐term storage and annealing due to a barrier for NP agglomeration, Ag oxidation, and impurity diffusion provided by the SiO2 shell. 相似文献
6.
对蓝宝石衬底上的InGaN/GaN和InGaN/AlGaN多量子阱结构和经激光剥离去除衬底的InGaN/GaN和InGaN/AlGaN多量子阱结构薄膜样品,进行了光致发光谱、高分辨XRD和喇曼光谱测量.PL测量结果表明,相对于带有蓝宝石衬底的样品,InGaN/GaN多量子阱薄膜样品的PL谱峰值波长发生较小的蓝移,而InGaN/AlGaN多量子阱薄膜样品的PL谱峰值波长发生明显的红移;喇曼光谱的结果表明,激光剥离前后E2模的峰值从569.1减少到567.5cm-1.这说明激光剥离去除衬底使得外延层整体的压应力得到部分释放,但InGaN/GaN与InGaN/AlGaN多量子阱结构中阱层InGaN的应力发生了不同的变化.XRD的结果证实了这一结论. 相似文献
7.
用SiO2纳米图形层作为模板在以蓝宝石为衬底的n-GaN单晶层上制备了InGaN/GaN多量子阱纳米线,并成功实现了其发光二极管器件(LED).场发射扫描电子显微镜(FESEM)的测量结果表明,InGaN/GaN多量子阱纳米线具有光滑的表面形貌和三角形的剖面结构.室温下阴极射线荧光谱(CL)的测试发现了位于461 nm... 相似文献
8.
I. A. Buyanova M. Izadifard L. Storasta W. M. Chen Jihyun Kim F. Ren G. Thaler C. R. Abernathy S. J. Pearton C. -C. Pan G. -T. Chen J. -I. Chyi J. M. Zavada 《Journal of Electronic Materials》2004,33(5):467-471
(Ga,Mn)/N/InGaN multiquantum well (MQW) diodes were grown by molecular beam epitaxy (MBE). The current-voltage characteristics
of the diodes show the presence of a parasitic junction between the (Ga,Mn)N and the n-GaN in the top contact layer due to
the low conductivity of the former layer. Both the (Ga,Mn)N/InGaN diodes and control samples without Mn doping show no or
very low (up to 10% at the lowest temperatures) optical (spin) polarization at zero field or 5 T, respectively. The observed
polarization is shown to correspond to the intrinsic optical polarization of the InGaN MQW, due to population distribution
between spin sublevels at low temperature, as separately studied by resonant optical excitation with a photon energy lower
than the bandgap of both the GaN and (Ga,Mn)N. This indicates efficient losses in the studied structures of any spin polarization
generated by optical spin orientation or electrical spin injection. The observed vanishing spin injection efficiency of the
spin light-emitting diode (LED) is tentatively attributed to spin losses during the energy relaxation process to the ground
state of the excitons giving rise to the light emission. 相似文献
9.
Hyung Koun Cho Jeong Yong Lee Chi Sun Kim Gye Mo Yang 《Journal of Electronic Materials》2001,30(10):1348-1352
We have studied the influence of indium (In) composition on the structural and optical properties of Inx Ga1−xN/GaN multiple quantum wells (MQWs) with In compositions of more than 25% by means of high-resolution x-ray diffraction (HRXRD),
photoluminescence (PL), and transmission electron microscopy (TEM). With increasing the In composition, structural quality
deterioration is observed from the broadening of the full width athalf maximum of the HRXRD superlattice peak, the broad multiple
emission peaks oflow temperature PL, and the increase of defect density in GaN capping layers and InGaN/GaN MQWs. V-defects,
dislocations, and two types of tetragonal shape defects are observed within the MQW with 33% In composition by high resolution
TEM. In addition, we found that V-defects result in different growth rates of the GaN barriers according to the degree of
the bending of InGaN well layers, which changes the period thickness of the superlattice and might be the source of the multiple
emission peaks observed in the InxGa1−xN/GaN MQWs with high in compositions. 相似文献
10.
D. I. Florescu D. S. Lee S. M. Ting J. C. Ramer E. A. Armour 《Journal of Electronic Materials》2003,32(11):1330-1334
The edge-emitting electroluminescence (FL) state of polarization of blue and green InGaN/GaN light-emitting diodes (LEDs)
grown in EMCORE’s commercial reactors was studied and compared to theoretical evaluations. Blue (∼475 nm) LEDs exhibit strong
EL polarization, up to a 3:1 distinction ratio. Green (∼530 nm) LEDs exhibit smaller ratios of about 1.5:1. Theoretical evaluations
for similar InGaN/GaN superlattices predicted a 3:1 ratio between light polarized perpendicular (E⊥c) and light polarized
parallel (E‖c) to the c axis. For the blue LEDs, a quantum well-like behavior is suggested because the E⊥c mode dominates
the E‖c mode 3:1. In contrast, for the green LEDs, a mixed quantum well (QW)-quantum dot (QD) behavior is proposed, as the
ratio of E⊥c to E‖c modes drops to 1.5:1. The EL polarization fringes were also observed, and their occurrence may be attributed
to a symmetric waveguide-like behavior of the InGaN/GaN LED structure. A large 40%/50% drop in the surface root mean square
(RMS) from atomic force microscopy (AFM) scans on blue/green LEDs with and without EL fringes points out that better surfaces
were achieved for the samples exhibiting fringing. At the same time, a 25%/10% increase in the blue/green LED photoluminescence
(PL) intensity signal was found for samples displaying EL interference fringes, indicating superior material quality and improved
LED structures. 相似文献
11.
C. Yuan T. Salagaj W. Kroll R. A. Stall M. Schurman C. Y. Hwang Y. Li W. E. Mayo Y. Lu S. Krishnankutty R. M. Kolbas 《Journal of Electronic Materials》1996,25(5):749-753
High quality InGaN thin films and InGaN/GaN double heterojunction (DH) structures have been epitaxially grown on c-sapphire
substrates by MOCVD in a production scale multi-wafer-rotating-disc reactor between 770 to 840°C. We observed that shroud
flow (majority carrier gas in the reaction chamber) is the key to obtaining high quality InGaN thin films. High purity H2 as the shroud flow results in poor crystal quality and surface morphology but strong photolumines-cence (PL) at room temperature.
However, pure N2 as the shroud flow results in high crystal quality InGaN with an x-ray full width at half maximum (FWHM)InGaN(0002) of 7.5 min and a strong room temperature PL peaking at 400 nm. In addition, InGaN/GaN single heterojunction (SH) and DH structures
both have excellent surface morphology and sharp interfaces. The full width at half maximum of PL at 300K from an InGaN/GaN
DH structure is about 100 meV which is the best reported to date. A high indium mole fraction in InGaN of 60% and high quality
zinc doped InGaN depositions were also achieved. 相似文献
12.
I. K. Shmagin J. F. Muth R. M. Kolbas S. Krishnankutty S. Keller A. C. Abare L. A. Coldren U. K. Mishra S. P. Den Baars 《Journal of Electronic Materials》1997,26(3):325-329
Photoluminescence (PL) characteristics of GaN/lnGaN/GaN single quantum wells (QWs) and an InGaN/GaN single heterojunction were studied using continuous wave (CW) and pulsed photoluminescence in both edge and surface emitting configurations. Samples were grown on c-plane sapphire substrates by atmospheric pressure metalorganic chemical vapor deposition (MOCVD). Room temperature and 77K PL measurements were performed using a CW Ar-ion laser (305 nm) and a frequency tripled (280 nm), pulsed, mode-locked Ti: sapphire laser. CW PL emission spectra from the quantum wells (24, 30, 80Å) were all blue shifted with respect to the reference sample. The difference (i. e., the blue shift) between the measured value of peak emission energy from the QW and the band-edge emission from the reference sample was attributed to quantum size effects, and to strain arising due to a significant lattice mismatch between InGaN and GaN. In addition, stimulated emission was observed from an InGaN/GaN single heterojunction in the edge and surface emitting configu-ration at 77K. The narrowing of emission spectra, the nonlinear dependence of output emission intensity on input power density, and the observation of a strongly polarized output are presented. 相似文献
13.
In this study, we fabricated and characterized an InGaN/GaN multi-quantum-well (MQW)-based p-n junction photodetector (PD) for voltage-selective light-emitting and photo-detective applications. The photode-tector exhibits a cutoff wavelength at around 460nm which is close to its electroluminescence (EL) peak position. The rejection ratio was determined to be more than three orders of magnitude. Under zero bias, the responsivity of the device peaks at 371 nm, with a value of 0.068 A/W, corresponding to a 23% quantum efficiency.The overall responsivity gradually rises as a function of reverse bias, which is explained by the enhanced photocarrier collection efficiency. 相似文献
14.
This paper describes the microstructure of ohmic contacts to an AlGaN/GaN heterostructure, of interest for high power transistors, and an analysis of V-defects in an InGaN/GaN multi-quantum well (MQW) light-emitting structure. A combination of different transmission electron microscopy (TEM) techniques has been employed, as they provide complementary information. These include bright field and dark field TEM, high-resolution electron microscopy, X-ray mapping, energy filtered TEM and high angle annular dark field. A full determination of the phase distribution in the ohmic contacts was achieved. The onset of low contact resistance was found to correspond with the formation of an interfacial layer containing both TiN and AlN, and of an intermetallic layer containing Al, Ti and Au in contact with it. The MQW structures were capped with a p-type GaN layer, and TEM and ADF studies of the samples show a number of V-defects 100-200 nm apart along the MQW. Each V-defect incorporates a pure edge (b = 1/3 <11-20>) dislocation, which runs through its apex up to the free surface. The defects contain GaN with no InGaN layers, suggesting the V-pits have been filled in by the capping layer. 相似文献
15.
Nitride-based near-ultraviolet multiple-quantum well light-emitting diodes with AlGaN barrier layers
C. H. Kuo S. J. Chang Y. K. Su L. W. Wu J. K. Sheu T. C. Wen W. C. Lai J. M. Tsai S. C. Chen 《Journal of Electronic Materials》2003,32(5):415-418
The In0.05Ga0.95N/GaN, In0.05Ga0.95N/Al0.1Ga0.9N, and In0.05Ga0.95N/Al0.18Ga0.82N multiple-quantum well (MQW) light-emitting diodes (LEDs) were prepared by metal-organic chemical-vapor deposition. (MOCVD).
It was found that the 20-mA electroluminescence (EL) intensity of the InGaN/Al0.1Ga0.9N MQW LED was two times larger than that of the InGaN/GaN MQW LED. The larger maximum-output intensity and the fact that maximum-output
intensity occurred at a larger injection current suggest that Al0.1Ga0.9N-barrier layers can provide a better carrier confinement and effectively reduce leakage current. In contrast, the EL intensity
of the InGaN/Al0.18Ga0.82N MQW LED was smaller because of the relaxation that occurred in the MQW active region of the sample. 相似文献
16.
The temperature dependence of performance of InGaN/GaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) with different indium compositions in the MQWs was investigated. With increasing In composition in the MQWs, the optical performance of the LEDs at room temperature was increased due to an increase in the localized energy states caused by In composition fluctuations in MQWs. As the temperature was increased, however, the decrease in output power for LED with a higher In composition in the MQWs was higher than that of LED with a lower In composition in the MQWs. This could be due to the increased nonradiation recombination through the high defect densities in the MQWs resulted from the increased accumulation of strain between InGaN well and GaN barrier. 相似文献
17.
18.
B. Schineller P. H. Lim G. P. Yablonskii E. V. Lutsenko O. Schön H. Protzmann M. Heuken K. Heime 《Journal of Electronic Materials》2000,29(1):31-36
We investigated the influence of doping and InGaN layer thickness on the emission wavelength and full width at half maximum
(FWHM) of InGaN/GaN single quantum wells (SQW) of thicknesses between 1 nm and 5 nm by temperature and intensity resolved
photoluminescence (PL). The crystalline quality of the GaN claddings was assessed by low temperature PL. The emission energy
of 5 nm Si doped SQW could be tuned from 3.24 eV to 2.98 eV by reducing the deposition temperature. An increase of piezoelectric
(PE) field screening with increasing deposition temperature is attributed to an increase of the SiH4 decomposition efficiency. Piezoelectric (PE) fields between 0.5 MV/cm and 1.2 MV/cm in undoped structures of varying SQW
thicknesses were calculated. Two activation energies of 15 meV and 46 meV of the SQW emission could be observed in temperature
resolved measurements. The higher value was assigned to the confined exciton binding energy, whereas the activation energy
of 15 meV is probably due to a decrease in carrier supply from the absorption zone in the GaN cladding into the SQW. 相似文献
19.
Kenji Uchida Masahiko Kawata Tao Yang Shigeo Goto Tomoyoshi Mishima Atsuko Niwa Jun Gotoh 《Journal of Electronic Materials》1999,28(3):246-251
We have examined how a growth interruption, caused by closing group-III sources, affects the crystalline quality of InGaN/GaN
quantum-well (QW) structures grown by metalorganic vapor phase epitaxy. The QW samples were characterized by their photoluminescence
(PL), and by atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy dispersive x-ray (EDX) microanalysis.
The PL peak wavelength was strongly dependent on the duration of the growth interruption and on the number of QW layers. AFM
measurements revealed that the size of the open hexagonally shaped pits in the QW structures increased dramatically as the
interruption duration was lengthened. Through TEM and EDX microanalysis, we found that the formation of these hexahedronal
pits, formed due to the growth interruption, causes a large fluctuation in the In composition, especially around the pits,
and the presence of such pits in an underlying QW layer strongly affects the In incorporation into the upper QW layers, leading
to significant growth-rate variation in an InGaN QW layer and red-shifting of the PL spectra when a multiple-QW structure
is grown. 相似文献
20.
纳米柱GaN基多量子阱(MQW)拥有量子尺寸效应以及应变释放等特性,对于提高GaN基发光二极管(LED)的发光效率具有重要意义.采用快速热退火(RTA)形成的自组装Ni纳米颗粒作为刻蚀掩膜,利用电感耦合等离子体反应离子刻蚀(ICP-RIE)制备纳米柱InGaN/GaN MQW.通过改变RTA温度发现在800℃以上才能有效形成Ni纳米颗粒掩膜.不同的ICP和射频(RF)功率条件下制备的纳米柱MQW光致发光强度相比于相同结构的平面MQW会发生显著变化.通过优化ICP-RIE的刻蚀条件,可以获得发光强度显著提高的纳米柱MQW结构.同时,纳米柱MQW中压电极化场的减弱会形成光致发光峰位蓝移. 相似文献