共查询到20条相似文献,搜索用时 328 毫秒
1.
V. V. Strelchuk V. P. Kladko E. A. Avramenko O. F. Kolomys N. V. Safryuk R. V. Konakova B. S. Yavich M. Ya. Valakh V. F. Machulin A. E. Belyaev 《Semiconductors》2010,44(9):1199-1210
High-resolution X-ray diffraction analysis and scanning confocal Raman spectroscopy are used to study the spatial distribution
of strains in the In
x
Ga1 − x
N/GaN layers and structural quality of these layers in a multilayered light-emitting diode structure produced by metal-organic
chemical vapor deposition onto (0001)-oriented sapphire substrates. It is shown that elastic strains almost completely relax
at the heterointerface between the thick GaN buffer layer and In
x
Ga1 − x
N/GaN buffer superlattice. It is established that the GaN layers in the superlattice are in a stretched state, whereas the
alloy layers are in a compressed state. In magnitude, the stretching strains in the GaN layers are lower than the compressive
strains in the InGaN layers. It is shown that, as compared to the buffer layers, the layers of the superlattice contain a
smaller number of dislocations and the distribution of dislocations is more randomly disordered. In micro-Raman studies on
scanning through the thickness of the multilayered structure, direct evidence is obtained for the asymmetric gradient distributions
of strains and crystal imperfections of the epitaxial nitride layers along the direction of growth. It is shown that the emission
intensity of the In
x
Ga1 − x
N quantum well is considerably (more than 30 times) higher than the emission intensity of the GaN barrier layers, suggesting
the high efficiency of trapping of charge carriers by the quantum well. 相似文献
2.
Z. Chen N. Fichtenbaum D. Brown S. Keller U.K. Mishra S.P. Denbaars S. Nakamura 《Journal of Electronic Materials》2008,37(5):546-549
In this report, the influence of magnesium doping on the characteristics of InGaN/GaN multiple quantum wells (MQWs) was investigated
by means of atomic force microscopy (AFM), photoluminescence (PL), and X-ray diffraction (XRD). Five-period InGaN/GaN MQWs
with different magnesium doping levels were grown by metalorganic chemical vapor deposition. The AFM measurements indicated
that magnesium doping led to a smoother surface morphology. The V-defect density was observed to decrease with increasing
magnesium doping concentration from ∼109 cm−2 (no doping) to ∼106 cm−2 (Cp2Mg: 0.04 sccm) and further to 0 (Cp2 Mg: 0.2 sccm). The PL measurements showed that magnesium doping resulted in stronger emission, which can be attributed to
the screening of the polarization-induced band bending. XRD revealed that magnesium doping had no measurable effect on the
indium composition and growth rate of the MQWs. These results suggest that magnesium doping in MQWs might improve the optical
properties of GaN photonic devices. 相似文献
3.
In this paper, we report the effect of using a group-V residual source evacuation (RSE) time on the interfaces of InGaAs/lnGaAsP
quantum wells (QWs) grown by gas-source molecular beam epitaxy. High-resolution x-ray rocking curve and low-temperature photoluminescence
(PL) were used to characterize the material quality. By optimizing the RSE time, a PL line width at 15K as narrow as 6.6 meV
is observed from a 2 nm wide single QW, which is as good as or better than what has been reported for this material system.
Very sharp and distinct satellite peaks as well as Pendellosung fringes are observed in the x-ray rocking curves of InxGa1−xAs/InxGa1−xASyP1−y multiple QWs, indicating good crystalline quality, lateral uniformity, and vertical periodicity. Theoretical considerations
of the PL linewidths of InxGa1−xAs/InxGa1−xASyP1−y single QWs show that for QW structures grown with the optimized RSE time, the PL linewidth is mainly due to alloy scattering,
whereas the contribution from interface roughness is small, indicating a good interface control. 相似文献
4.
郭洪英 孙元平 Yong-Hoon Cho Eun-Kyung Suh Hai-Joon Lee Rak-Jun Choi Yoon-Bong Hahn 《半导体学报》2012,33(5):053001-4
利用光荧光、阴极荧光以及时间分辨荧光光谱技术研究了具有不同In组分的渐变InGaN/GaN多量子阱结构中的相分凝现象。在10 K的荧光光谱中,所有的三个样品中除了主发光峰位外,在其高能及低能位置处还出现了另外两个发光峰,表现出了明显的相分凝现象。三个样品阴极荧光结果中呈现出了明显的强度对比,证明了相分凝现象随着量子阱中In组分的增加而加剧。在15 K的时间分辨荧光光谱中,随着In组分的增加,谱线的上升时间得到了延迟,这表明了载流子在由于相分凝而造成的低、高In组分结构中的输运。 相似文献
5.
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
6.
《Microelectronics Journal》2007,38(6-7):767-770
The influence of Si doping on the photoluminescence (PL) properties of (Al0.3Ga0.7)0.5In0.5P/Ga0.5In0.5P multiple-quantum-wells (MQWs) was studied. For the samples without p-type layers, the PL peak wavelength from (Al0.3Ga0.7)0.5In0.5P/Ga0.5In0.5P MQWs did not vary when Si was doped in MQWs, the PL peak intensity did not change obviously and the PL FWHM broadened. We consider that Si doping results in worse interface quality of (Al0.3Ga0.7)0.5In0.5P/Ga0.5In0.5P MQWs. However, for the full light-emitting diode (LED) structure samples, the PL intensity of MQWs obviously increased when Si was doped in MQWs. The PL intensity from MQWs with Si-doped barriers was about 13 times stronger than that of undoped MQWs. The PL intensity from MQWs with Si-doped barriers and wells was strong as 28 times as that of undoped MQWs. The reasons are discussed. 相似文献
7.
Digital alloying using molecular beam epitaxy (MBE) was investigated to produce AlGaInP quaternary alloys for bandgap engineering useful in 600-nm band optoelectronic device applications. Alternating Ga0.51In0.49P/Al0.51In0.49P periodic layers ranging from 4.4 monolayers (ML) to 22.4 ML were used to generate 4,000-Å-thick (Al0.5Ga0.5)0.51In0.49P quaternary materials to understand material properties as a function of constituent superlattice layer thickness. High-resolution x-ray diffraction (XRD) analysis exhibited fine satellite peaks for all the samples confirming that digitally-alloyed (Al0.5Ga0.5)0.51In0.49P preserved high structural quality consistent with cross-sectional transmission electron microscopy (X-TEM) images. Low-temperature photoluminescence (PL) measurements showing a wide span of luminescence energies ~ 170 meV can be obtained from a set of identical composition digitally-alloyed (Al0.5Ga0.5)0.51In0.49P with different superlattice periods, indicating the bandgap tunability of this approach and its viability for III-P optoelectronic devices grown by MBE. 相似文献
8.
Nucleation kinetics during the growth of InxGa1−xN on a GaN substrate have been studied. The behavior of nonequilibrium between the InxGa1−xN and the GaN substrate has been analyzed, and hence, the expression derived for the stress-induced supercooling/superheating
has been numerically evaluated. The maximum amount of stress-induced supercooling is found to be 1.017 K at x=0.12. These
values are incorporated in the classical heterogeneous nucleation theory. Using the regular solution model, the interfacial
tension between the nucleus and substrate and, hence, the interfacial tension between nucleus and mother phase and thermodynamical
potential of the compounds have been calculated. The amount of driving force available for the nucleation has been determined
for different compositions and degrees of supercooling. It has been shown that the value of the interaction parameter of InN-GaN
plays a dominant role in nucleation and growth kinetics of InxGa1−xN on a GaN substrate. These values have been used to evaluate the nucleation parameters. It is shown that the nucleation barrier
for the formation of a InxGa1−xN nucleus on a GaN substrate is minimum in the range of x=0.12 to x=0.17, and it has been qualitatively proved that good quality
InxGa1−xN on GaN can be grown only in the range 0<x≤0.2. 相似文献
9.
M. C. Johnson Z. Liliental-Weber D. N. Zakharov D. E. Mccready R. J. Jorgenson J. Wu W. Shan E. D. Bourret-Courchesne 《Journal of Electronic Materials》2005,34(5):605-611
Temperature-gradient metalorganic chemical vapor deposition (MOCVD) was used to deposit InxGa1−xN/GaN multiple quantum well (MQW) structures with a concentration gradient of indium across the wafer. These MQW structures
were deposited on low defect density (2×108 cm−2) GaN template layers for investigation of microstructural properties and V-defect (pinhole) formation. Room temperature (RT)
photoluminescence (PL) and photomodulated transmission (PT) were used for optical characterization, which show a systematic
decrease in emission energy for a decrease in growth temperature. Triple-axis x-ray diffraction (XRD), scanning electron microscopy,
and cross-sectional transmission electron microscopy were used to obtain microstructural properties of different regions across
the wafer. Results show that there is a decrease in crystal quality and an increase in V-defect formation with increasing
indium concentration. A direct correlation was found between V-defect density and growth temperature due to increased strain
and indium segregation for increasing indium concentration. 相似文献
10.
U. Zeimer U. Jahn V. Hoffmann M. Weyers M. Kneissl 《Journal of Electronic Materials》2010,39(6):677-683
The optical and structural properties of In0.08Ga0.92N/In0.02Ga0.98N multiple quantum wells (MQWs) grown at different temperatures and with different supplies of indium were analyzed by atomic
force microscopy and spectrally resolved cathodoluminescence (CL). By comparing the contrasts of monochromatic CL images with
high-resolution secondary-electron images of the sample surface, it is shown that almost all contrasts of the CL images can
be explained by lateral inhomogeneities of both the thickness and the InN mole fraction of the InGaN layers. Dark contrasts
in the CL images solely related to dislocations were not observed, indicating very weak nonradiative recombination correlated
with threading dislocations in the InGaN quantum wells. The lateral inhomogeneities of layer thickness and indium incorporation
depend strongly on the growth conditions. 相似文献
11.
P. Chavarkar S. K. Mathis L. Zhao S. Keller J. S. Speck U. K. Mishra 《Journal of Electronic Materials》2000,29(7):944-949
Strain relaxation of hypercritical thickness InxGa1−xAs layers has been observed during lateral oxidation of underlying AlAs layers. Strain relaxation of InxGa1−xAs layers was studied as a function of indium composition and the AlAs oxidation temperature. It is proposed that the enhanced
strain relaxation is due to two factors. The first is enhanced motion of threading dislocations due to stresses generated
during the lateral oxidation process. The second is the porous nature of the InxGa1−xAs/Al2O3 interface that minimizes the interaction of threading dislocations with existing misfit dislocation segments. The extent
of strain relaxation increases with increasing oxidation temperature, whereas the efficiency of strain relaxation was found
to decrease with increasing indium composition. The efficiency of strain relaxation upon oxidation can be improved by reducing
the misfit dislocation density at the InxGa1−xAs/AlAs interface prior to oxidation and by changing the nature of the InxGa1−xAs/Al2O3 interface. 相似文献
12.
I. P. Soshnikov V. V. Lundin A. S. Usikov I. P. Kalmykova N. N. Ledentsov A. Rosenauer B. Neubauer D. Gerthsen 《Semiconductors》2000,34(6):621-625
MOCVD-grown heterostructures with one or several InxGa1?x N layers in a GaN matrix have been studied by transmission electron microscopy. In heterostructures with thick InGaN layers, a noncoherent system of domains with lateral dimensions (~50 nm) on the order of the layer thickness (~40 nm) is formed. In the case of ultrathin InGaN inclusions, nanodomains coherent with the GaN matrix are formed. The content of indium in nanodomains, determined by the DALI method, is as high as x≈0.6 or more, substantially exceeding the average In concentration. The density of the nanodomains formed in the structures studied is n≈(2–5)×1011 cm?2. In the structures with ultrathin InGaN inclusions, two characteristic nanodomain sizes are observed (3–6 and 8–15 nm). 相似文献
13.
14.
High-quality AlxGa1−xAs layers with aluminum arsenide contentx up to 0.34 have been grown in a low pressure metalorganic chemical vapor deposition (MOCVD) system using trimethylgallium
(TMG), trimethylamine alane (TMAA) and arsine. The carbon content in these films depended on growth conditions but was in
general lower than in those obtained with trimethylaluminum (TMA) instead of TMAA in the same reactor under similar conditions.
Unlike TMA grown layers, the TMAA grown AlxGa1−xAs layers, (grown at much lower temperature—down to 650° C), exhibited room temperature photolu-minescence (PL). Low temperature
(25 K) PL from these films showed sharp bound exciton peaks with a line width of 5.1 meV for Al0.25Ga0.75As. A 39 period Al0.28Ga0.72As (5.5 nm)/GaAs (8.0 nm) superlattice grown at 650° C showed a strong PL peak at 25 K with a line width of 5.5 meV attesting
to the high quality of these layers. 相似文献
15.
Benjamin Reuters A. Wille B. Holländer E. Sakalauskas N. Ketteniss C. Mauder R. Goldhahn M. Heuken H. Kalisch A. Vescan 《Journal of Electronic Materials》2012,41(5):905-909
Quaternary barrier layers for GaN-based high-electron-mobility transistors (HEMT) have recently been a focus of interest because
of the possible lattice-matched growth to GaN. This results in a reduction of strain-related defects, while having the option
of adjusting the bandgap separately. A further benefit of the quaternary approach is the possibility to achieve high polarization
and high carrier mobility simultaneously. This may improve the performance of such devices beyond what is possible with ternary
barrier layers. In this work, we report on growth and characterization of Al
x
In
y
Ga1−x−y
N barrier layers within the range of 16% to 56% Al, 2% to 45% In, and 20% to 82% Ga deposited on conventional GaN buffer layers
on sapphire. We present an effective way to change the composition of quaternary layers and discuss the influence of tensile
and compressive strain on structural and electrical properties. From high-resolution x-ray diffraction (HRXRD), Rutherford
backscattering spectroscopy (RBS), and wavelength-dispersive x-ray spectroscopy (WDX), we determined the compositions and
strain states of the AlInGaN layers. The bandgaps (E
g) were obtained by spectroscopic ellipsometry (SE). Hall and van der Pauw measurements on thin heterostructure layers yielded
high mobilities in excess of 1550 cm2/V s and 5350 cm2/V s at room temperature and 77 K, respectively. 相似文献
16.
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
17.
H. Lakner G. Brockt C. Mendorf A. Radefeld F. Scholz V. Härle J. Off A. Sohmer 《Journal of Electronic Materials》1997,26(10):1103-1108
The low pressure metalorganic vapor phase epitaxy growth of wurzite (Al, In, Ga)N heterostructures on sapphire substrates
is investigated by quantitative analytical scanning transmission electron microscopy techniques like atomic number (Z-) contrast
imaging and convergent beam electron diffraction (CBED). Especially (In, Ga)N quantum wells of different thicknesses as well
as superlattices were analyzed with respect to defects, chemical composition variations, interface abruptness and strain (relaxation)
effects. The interfaces in In0.12Ga0.88N/GaN quantum wells appear to be asymmetric. Additionally, we found composition variations of ΔxIn≥0.03 within the InGaN quantum wells. The application of electron diffraction techniques (CBED) yields quantitative information
on strain and relaxation effects. For the case of 17 nm thick InGaN quantum wells, we observed relaxation effects which are
not present in the investigated thin quantum wells of 2 nm thickness. The experimentally obtained diffraction patterns were
compared to simulations in order to get values for strain within the quantum wells. Additionally, the influence of dislocations
on the digression of superlattices is investigated. 相似文献
18.
Shalini Lal Eric Snow Jing Lu Brian Swenson Stacia Keller Steven P. Denbaars Umesh K. Mishra 《Journal of Electronic Materials》2012,41(5):857-864
In this paper, we report the fabrication process and direct-current (DC) characteristics of a wafer-bonded heterostructure-based
vertical transistor. It comprises an In0.53Ga0.47As/In0.52Al0.48As/In0.53Ga0.47As field-effect transistor wafer-bonded to a Ga-polar In0.1Ga0.9N/GaN template. In the DC-bias operation of this device, the current conduction is initially confined lateral to the InGaAs
channel and then flows vertically through a conductive aperture defined in the InGaN/GaN layers. The narrow aperture is isolated
by ion-implanted current blocking layer (CBL) regions. The I
d–V
ds characteristics of the device demonstrate transistor-like behavior. Design optimizations have been applied to the implant
and doping conditions of the InGaN/GaN layers to eliminate the leakage paths through the CBL while simultaneously obtaining
unhindered current conduction through the aperture of the device. 相似文献
19.
W. E. Carlos E. R. Glaser T. A. Kennedy Shuji Nakamura 《Journal of Electronic Materials》1999,28(3):252-256
Photoluminescence (PL) based optically detected magnetic resonance (ODMR) studies as well as electroluminescence detected
and electrically detected magnetic resonance (ELDMR and EDMR, respectively) measurements of InxGa1−xN quantum wells were performed. In the ODMR, two PL-enhancing resonances were observed: an electron resonance and a hole resonance.
The electron resonance is consistent with expectations for the g value in bulk InxGa1−xN for x ≈ 0.4 but deviates significantly in an x≈0.3 sample. Possible reasons for this include the effects of strain and confinement.
The hole resonance is qualitatively similar to observations in Mg-doped GaN, but more isotropic in the x ≈ 0.3 diode than
in the x ≈ 0.4 sample. We measure relatively long radiative lifetimes (as long as ∼0.2 ms) in the ODMR which facilitate the
observation of the resonances and indicate that the electron and hole are spatially separated either by potential fluctuations
within the quantum well or by the trapping of the hole at an acceptor in the player of AlGaN whch serves as one of the confining
barriers. In the EDMR and ELDMR experiments, the signal is primarily due to a reduction in the nonradiative recombination
at resonance. While the ODMR is alwyas emission-enhancing, the ELDMR is luminescence-quenching, supporting the notion that
techniques are probing different centers. 相似文献
20.
J. A. Grenko C. L. ReynoldsJr. D. W. Barlage M. A. L. Johnson S. E. Lappi C. W. Ebert E. A. Preble T. Paskova K. R. Evans 《Journal of Electronic Materials》2010,39(5):504-516
We report on the growth of Al0.25Ga0.75N/GaN heterostructures grown on low dislocation density vicinal surfaces of semi-insulating c-axis GaN substrates. Atomic force microscopy (AFM), photoluminescence (PL), cathodoluminescence (CL), high-resolution x-ray
diffraction (HRXRD), secondary-ion mass spectroscopy (SIMS), Hall effect, and Raman spectroscopy have been used to assess
structural and electrical properties as a function of substrate offcut. Bulk GaN substrates with vicinal offcut between 0.5°
and 1.4° are optimal with respect to surface roughness and dopant incorporation. AFM, PL, and CL show decreasing Mg incorporation
with increasing offcut angle. Raman spectroscopy, used to analyze biaxial strain, confirms essentially strain-free heterostructure
growth on vicinal substrates with offcut angles between 0.5° and 1.4° off [0001] toward [1[`1] 00] [1\overline{1} 00] . Aluminum (Al) incorporation in the Al
x
Ga1−x
N barrier assessed by Raman vibration is in excellent agreement with trends found by HRXRD. 相似文献