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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.
InGaN基量子阱作为太阳电池器件的有源区时,垒层厚度设计以及实际生长对其光学特性的影响极为重要.采用金属有机化学气相沉积(MOVCD)技术,在蓝宝石衬底上外延生长了垒层厚度较厚的InGaN/GaN多量子阱,使用高分辨X射线衍射和变温光致发光谱研究了垒层厚度对InGaN多量子阱太阳电池结构的界面质量、量子限制效应及其光学特性的影响.较厚垒层的InGaN/GaN多量子阱的周期重复性和界面品质较好,这可能与垒层较薄时对量子阱的生长影响有关.同时,厚垒层InGaN/GaN多量子阱的光致发光光谱峰位随温度升高呈现更为明显的“S”形(红移-蓝移-红移)变化,表现出更强的局域化程度和更高的内量子效率. 相似文献
3.
The direction of the piezoelectric field in InGaN/GaN multiple quantum-well (MQW) structures grown by metal-organic vapor
deposition (MOCVD) was determined using excitation-power-density variable photoluminescence (PL). By comparing the excitation-power-density
dependence of the shift of the PL peak and the change of the full-width at half-maximum (FWHM) of the peak from an InGaN/GaN
MQW structure and an InGaN MQW-based light-emitting diode (LED), the piezoelectric field in the InGaN/GaN MQW structures was
unambiguously determined to be pointing toward the substrate. This result helps to identify the surface polarity of the LED
wafer as Ga-faced. 相似文献
4.
5.
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
6.
Effect of growth pressure on indium incorporation during the growth of InGaN by MOCVD 总被引:1,自引:0,他引:1
Dong-Joon Kim Yong-Tae Moon Keun-Man Song In-Hwan Lee Seong-Ju Park 《Journal of Electronic Materials》2001,30(2):99-102
The effect of the growth pressure on the In incorporation in InGaN thin films, grown by metalorganic chemical vapor deposition
(MOCVD) have been investigated. The InGaN thin films were grown by varying the growth pressures, while maintaining all other
growth parameters constant. Photoluminescence and high resolution x-ray diffraction (XRD) measurements showed that the In
incorporation in the InGaN thin film was drastically increased with decreasing growth pressures. XRD analysis also revealed
that the In concentration in the films was increased by 7.5% as the growth pressure was decreased from 250 torr to 150 torr.
This can be attributed to the enhanced mass transportation of precursor gases through the boundary-layer on the substrate
in the MOCVD system. 相似文献
7.
采用金属有机物化学气相淀积(MOCVD)技术,在蓝宝石衬底上生长了Al0.48Ga0.52N/Al0.54Ga0.36N多量子阱(MQWs)结构。通过双晶X射线衍射(DCXRD)、原子力显微镜(AFM)和阴极荧光(CL)等测试技术,分别对样品的结构和光学特性进行了表征。在DCXRD图谱中,可以观察到明显的MQWs衍射卫星峰,通过拟和,MQWs结构中阱和垒的厚度分别为2.1和9.4nm,Al组分分别为0.48和0.54。在AFM表面形貌图上,可以观察到清晰的台阶流,表明MQWs获得了二维生长;与此同时,MQWs结构存在一些裂缝,主要原因为AlGaNMQWs结构和下层GaN层间存在很大的应力。CL测试表明,AlGaNMQWs结构的发光波长为295nm,处于深紫外波段,同时观察到处于蓝光、绿光波段的缺陷发光。 相似文献
8.
J. Zhong G. Saraf H. Chen Y. Lu Hock M. Ng T. Siegrist A. Parekh D. Lee E. A. Armour 《Journal of Electronic Materials》2007,36(6):654-658
ZnO nanotips are grown on epitaxial GaN/c-sapphire templates by metalorganic chemical vapor deposition. X-ray diffraction
(XRD) studies indicate that the epitaxial relationship between ZnO nanotips and the GaN layer is (0002)ZnO||(0002)GaN and
(101̄0)ZnO||(101̄0)GaN. Temperature-dependent photoluminescence (PL) spectra have been measured. Sharp free exciton and donor-bound
exciton peaks are observed at 4.4 K with photon energies of 3.380 eV, 3.369 eV, and 3.364 eV, confirming high optical quality
of ZnO nanotips. Free exciton emission dominates at temperatures above 50 K. The thermal dissociation of these bound excitons
forms free excitons and neutral donors. The thermal activation energies of the bound excitons at 3.369 eV and 3.364 eV are
11 meV and 16 meV, respectively. Temperature-dependent free A exciton peak emission is fitted to the Varshni’s equation to
study the variation of energy bandgap versus temperature. 相似文献
9.
J.P. Liu J.B. Limb J.-H. Ryou W. Lee D. Yoo C.A. Horne R.D. Dupuis 《Journal of Electronic Materials》2008,37(5):558-563
Mg-doped InGaN/GaN p-type short-period superlattices (SPSLs) are developed for hole injection and contact layers of green light-emitting diodes
(LEDs). V-defect-related pits, which are commonly found in an InGaN bulk layer, can be eliminated in an InGaN/GaN superlattice
with thickness and average composition comparable to those of the bulk InGaN layer. Mg-doped InGaN/GaN SPSLs show significantly
improved electrical properties with resistivity as low as ∼0.35 ohm-cm, which is lower than that of GaN:Mg and InGaN:Mg bulk
layers grown under optimized growth conditions. Green LEDs employing Mg-doped InGaN/GaN SPSLs for hole injection and contact
layers have significantly lower reverse leakage current, which is considered to be attributed to improved surface morphology.
The peak electroluminescence intensity of LEDs with a SPSL is compared to that with InGaN:Mg bulk hole injection and contact
layers. 相似文献
10.
研究了Si掺杂对MOCVD生长的(Al0.3Ga0.7)In0.5P/Ga0.5In0.5P多量子阱发光性能的影响.样品分为两类:一类只生长了(Al0.3Ga0.7)In0.5P/Ga0.5In0.5P多量子阱结构;另一类为完整的多量子阱LED结构.对于只生长了(Al0.3Ga0.7)In0.5P/Ga0.5In0.5P多量子阱结构的样品,掺Si没有改变量子阱发光波长,但使得量子阱发光强度略有下降,发光峰半高宽明显增大.这应是掺Si使量子阱界面质量变差导致的.而在完整LED结构的情况下,掺Si却大大提高了量子阱的发光强度.相对于未掺杂多量子阱LED结构,垒层掺Si使多量子阱的发光强度提高了13倍,阱层和垒层均掺Si使多量子阱的发光强度提高了28倍,并对这一现象进行了讨论. 相似文献
11.
12.
A. M. Jones M. L. Osowski R. M. Lammert J. A. Dantzig J. J. Coleman 《Journal of Electronic Materials》1995,24(11):1631-1636
A computational diffusion model is used to predict thickness and composition profiles of ternary InxGa1-xAs quantum wells grown by selective-area, atmospheric pressure metalorganic chemical vapor deposition (MOCVD), and its accuracy
is investigated. The model utilizes diffusion equations and boundary conditions derived from basic MOCVD theory, with reaction
parameters derived from experimental results, to predict the concentration of each column III constituent throughout the concentration
boundary layer. Solutions to these equations are found using the two-dimensional, finite element method. The growth thickness
profiles of GaAs, InP, and InxGa1-xAs deposited by selective-area MOCVD are observed by conventional profilometry, and compositions are measured indirectly by
laser emission wavelengths. The data presented show that the model accurately predicts growth thickness and composition profiles
of ternary III-V materials grown by selective-area MOCVD. 相似文献
13.
利用MOCVD系统在Al2O3衬底上生长InGaN材料和InGaN/GaN量子阱结构材料,研究发现InGaN材料中In组份几乎不受TMG与TMI的流量比的影响,而只与生长温度有关,生长温度由800℃降低到740℃,In组份的从0.22增加到0.45;室温InGaN光致发光光谱(PL)峰全半高宽(FWHM)为15.5nm;InGaN/GaN量子阱区InGaN的厚度2nm,但光荧光的强度与100nm厚InGaN的体材料相当。 相似文献
14.
B. P. Keller S. Keller D. Kapolnek W. N. Jiang Y. F. Wu H. Masui X. Wu B. Heying J. S. Speck U. K. Mishra S. P. Denbaars 《Journal of Electronic Materials》1995,24(11):1707-1709
Hall mobilities as high as 702 and 1230 cm2/Vs at 300 and 160K along with low dislocation densities of 4.0 × 108 cm-2 have been achieved in GaN films grown on sapphire by metalorganic chemical vapor deposition. High growth temperatures have
been established to be crucial for optimal GaN film quality. Photoluminescence measurements revealed a low intensity of the
deep defect band around 550 nm in films grown under optimized conditions. 相似文献
15.
The abruptness of hetero-interfaces in InGaN multiple quantum well structures is shown to degrade when a high temperature
growth follows growth of the multiple quantum well (MQW) region, as is generally required for the growth of full device structures.
We have analyzed MQW samples both with and without high temperature GaN “cap” layers, using x-ray diffraction (XRD), grazing
incidence x-ray reflection (GIXR), and photoluminescence. While all of these techniques indicate a degradation of the MQW
structure when it is followed by growth at high temperature, GIXR is shown to be especially sensitive to changes of heterointerface
abruptness. GIXR measurements indicate that the heterojunctions are less abrupt in samples that have high temperature cap
layers, as compared to samples with no cap layer. Furthermore, the degree of roughening is found to increase with the duration
of growth of the high temperature cap layer. The degradation of the heterointerfaces is also accompanied by a reduction in
the intensity of satellite peaks in the x-ray diffraction spectrum. 相似文献
16.
Roskowski A. M. Preble E. A. Einfeldt S. Miraglia P. M. Davis R. F. 《Journal of Electronic Materials》2002,31(5):421-428
High-resolution x-ray diffraction (XRD) and atomic force microscopy (AFM) of pendeo-epitaxial (PE) GaN films confirmed transmission
electron microscopy (TEM) results regarding the reduction in dislocations in the wings. Wing tilt ≤0.15° was due to tensile
stresses in the stripes induced by thermal expansion mismatch between the GaN and the SiC substrate. A strong D°X peak at
≈3.466 eV (full-width half-maximum (FWHM) ≤300 μeV) was measured in the wing material. Films grown at 1020°C exhibited similar
vertical [0001] and lateral [11
0] growth rates. Increasing the temperature increased the latter due to the higher thermal stability of the GaN(11
0). The (11
0) surface was atomically smooth under all growth conditions with a root mean square (RMS)=0.17 nm. 相似文献
17.
The impact of nitridation and nucleation layer process conditions on morphology and electron transport in GaN epitaxial films 总被引:1,自引:0,他引:1
A. E. Wickenden D. D. Koleske R. L. Henry R. J. Gorman J. C. Culbertson M. E. Twigg 《Journal of Electronic Materials》1999,28(3):301-307
A systematic study has been performed to determine the characteristics of an optimized nucleation layer for GaN growth on
sapphire. The films were grown during GaN process development in a vertical close-spaced showerhead metalorganic chemical
vapor deposition reactor. The relationship between growth process parameters and the resultant properties of low temperature
GaN nucleation layers and high temperature epitaxial GaN films is detailed. In particular, we discuss the combined influence
of nitridation conditions, V/III ratio, temperature and pressure on optimized nucleation layer formation required to achieve
reproducible high mobility GaN epitaxy in this reactor geometry. Atomic force microscopy and transmission electron microscopy
have been used to study improvements in grain size and orientation of initial epitaxial film growth as a function of varied
nitridation and nucleation layer process parameters. Improvements in film morphology and structure are directly related to
Hall transport measurements of silicon-doped GaN films. Reproducible growth of silicon-doped GaN films having mobilities of
550 cm2/Vs with electron concentrations of 3 × 1017 cm−3, and defect densities less than 108 cm−2 is reported. These represent the best reported results to date for GaN growth using a standard two-step process in this reactor
geometry. 相似文献
18.
R. Niebuhr K. H. Bachem U. Kaufmann M. Maier C. Merz B. Santic P. Schlotter H. Jürgensen 《Journal of Electronic Materials》1997,26(10):1127-1130
Oxygen doped GaN has been grown by metalorganic chemical vapor deposition using N2O as oxygen dopant source. The layers were deposited on 2″ sapphire substrates from trimethylgallium and especially dried
ammonia using nitrogen (N2) as carrier gas. Prior to the growth of the films, an AIN nucleation layer with a thickness of about 300? was grown using
trimethylaluminum. The films were deposited at 1085°C at a growth rate of 1.0 μm/h and showed a specular, mirrorlike surface.
Not intentionally doped layers have high resistivity (>20 kW/square). The gas phase concentration of the N2O was varied between 25 and 400 ppm with respect to the total gas volume. The doped layers were n-type with carrier concentrations
in the range of 4×1016 cm−3 to 4×1018 cm−3 as measured by Hall effect. The observed carrier concentration increased with increasing N2O concentration. Low temperature photoluminescence experiments performed on the doped layers revealed besides free A and B
exciton emission an exciton bound to a shallow donor. With increasing N2O concentration in the gas phase, the intensity of the donor bound exciton increased relative to that of the free excitons.
These observations indicate that oxygen behaves as a shallow donor in GaN. This interpretation is supported by covalent radius
and electronegativity arguments. 相似文献
19.
InGaN layers were grown on GaN films by flow modulation epitaxy (FME) using the precursors trimethylgallium, trimethylindium,
and ammonia. The indium composition of the FME grown layers was generally lower than of films grown under the same conditions
in the continuous growth mode, but which had been of poor optical quality. The indium incorporation efficiency increased with
decreasing ammonia flush time, increasing ammonia flow during group-III injection, and increasing group-III precursor injection
time. Films grown under optimized conditions showed intense band edge related luminescence at room temperature up to a wavelength
of 465 nm. Atomic force microscopy investigations revealed a strong dependence of the surface morphology of the InGaN films
on the growth mode. 相似文献
20.
用低压MOCVD生长应变InGaAs/GaAs量子阱,采用中断生长、应变缓冲层(SBL)、改变生长速度和调节Ⅴ/Ⅲ等方法改善InGaAs/GaAs量子阱的光致发光(PL)质量。PL结果表明,10s生长中断结合适当的SBL生长的量子阱PL谱较好。该量子阱应用于1.06μm激光器的制备,未镀膜的宽条激光器(100μm×1000μm)有低阈值电流密度(110A/cm2)和高的斜率效率(0.256W/A,per.facet)。 相似文献