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1.
The polarization of the photoluminescence (PL) of self-assembled CdSe quantum dots (QDs), grown by metalorganic chemical vapor
phase deposition, was measured. From the (001) surface, the PL was found preferentially polarized in the
direction, while from the
cleaved surface in the [001] direction. The polarization of PL depends strongly on the ZnSe capping layer thickness and the
PL energy. With an increase in ZnSe coverage, the intensity ratio
was found to increase first, then decrease after the coverage is thicker than a critical value. Moreover, such a critical
thickness is smaller for larger QDs (lower PL energies). Possible origins of the PL polarization are discussed. We suggest
that besides the quantum confinement effects, the strain field in the QDs also plays an essential role in the observed polarization
of PL. 相似文献
2.
X. B. Zhang J. H. Ryou R. D. Dupuis L. He R. Hull G. Walter N. Holonyak Jr. 《Journal of Electronic Materials》2006,35(4):701-704
Multiple-stacked InP self-assembled quantum dots (SAQD or QD) were grown on an In0.5Al0.3Ga0.2P matrix lattice-matched on a GaAs (001) substrate using metalorganic chemical vapor deposition. Cathodoluminescence (CL)
scanning electron microscopy, and transmission electron microscopy were employed to characterize the optical, morphological,
and structural properties of the grown QDs. We found that the CL line width broadens and the surface becomes rough with an
increase in the number of stacked QD layers in the structure. However, by introducing thin tensile-strained Al0.6Ga0.4P layers in the middle of In0.5Al0.3Ga0.2P spacer layers to compensate the compressive strain of the InP QD layers, the CL and morphology are significantly improved.
Using this technique, 30-stacked InP/In0.5Al0.3Ga0.2P QD structures with improved CL properties and surface morphology were realized. 相似文献
3.
InGaAs quantum dots formed in tetrahedral-shaped recesses on GaAs (111)B grown by metalorganic chemical vapor deposition 总被引:1,自引:0,他引:1
Yoshiki Sakuma Masashi Shima Yuji Awano Yoshiro Sugiyama Toshiro Futatsugi Naoki Yokoyama Kazuhito Uchida Noboru Miura Takashi Sekiguchi 《Journal of Electronic Materials》1999,28(5):466-480
Novel semiconductor quantum dots (QDs), grown in tetrahedral-shaped recesses (TSRs) formed on a (111)B GaAs substrate, are
described from both material science and device application points of view. After explaining the fabrication procedure for
TSRs, growth of InGaAs QDs and their optical properties are explained. It is revealed that an InGaAs QD of indium-rich chemical
composition is formed spontaneously at the bottom of each TSR. The mechanism of the QD formation is discussed in detail. It
is proved from magneto-photoluminescence that the QDs actually have optical properties peculiar to zero-dimensional confinement.
Several experimental results indicating excellent growth controllability of the QDs are presented. Finally, recent challenges
to apply the QDs to electronic memory devices are reported. Two kinds of devices, where the position of individual QD is artificially
controlled, are proposed for the first time and the preliminary experimental results are explained. 相似文献
4.
We report the characteristics of ternary InAlP and InGaP self-assembled quantum dots grown by metalorganic chemical vapor
deposition. The structural and optical properties of these ternary quantum dots are compared with the characteristics of binary
InP quantum dots grown under similar conditions. Because these ternary quantum dots have different bandgaps, strain, and composition
compared to binary InP quantum dots, the ternary quantum-dot optical and physical properties are markedly different. The quantum-dot
structures are grown uncapped (exposed QDs) and capped (embedded QDs) and characterized by atomic force microscopy (AFM) and
photoluminescence (PL). InAlP quantum dots have higher densities and smaller sizes and InGaP quantum dots have smaller densities,
as compared with InP quantum dots grown under similar conditions. Also, a random and broad size distribution is observed for
InGaP quantum dots and the luminescence from InGaP dots is broader than for InP quantum dots. 相似文献
5.
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
6.
In0.5Al0.5P lattice-matched to GaAs and In0.5A10.5As lattice-matched to InP epilayers were grown by atmospheric pressure metalorganic chemical vapor deposition (AP-MOCVD).
The effect of trimethylindium on the purity of the as-grown layers was systematically studied using secondary ion mass spectroscopy
(SIMS), deep level transient spectroscopy (DLTS), and capacitance-voltage (C-V) measurements. The SIMS results showed that
oxygen is the main impurity in all layers and the oxygen concentration in InAlP was approximately one to four orders of magnitude
higher than the oxygen concentration found in InALAs when the same indium source was used, indicating that more oxygen was
introduced by the phosphine source than by the arsine source. Two electron traps in the InAlP epilayers and four electron
traps in the InALAs epilayers were observed in this study. When a high-purity indium source was used, the best InAlP epilayer
showed only one deep electron trap at 0.50 eV while the best InALAs epilayer showed no deep levels measured by DLTS. In addition,
we also found that a high concentration of oxygen is related to the high resistivity in both material systems; this suggests
that semi-insulating (SI) materials can be achieved by oxygen doping and high quality conducting materials can only be obtained
through the reduction of oxygen. The oxygen concentration measured by SIMS in the best InALAs epilayer was as low as 3 × 1017 cm−3. 相似文献
7.
Yugang Zhou Deliang Wang Rongming Chu Chak-Wah Tang Yundong Qi Zhengdong Lu Kevin J. Chen Kei May Lau 《Journal of Electronic Materials》2005,34(1):112-118
The correlation between the resistivity of an undoped GaN/Al2O3 interfacial layer and in-situ reflectance spectrum in metalorganic chemical vapor deposition and the mechanism of this correlation
were investigated. The first minimum reflectance during the initial high-temperature GaN growth was found to be a good indicator
of the resistivity of the GaN buffer. The background electron concentration and mobility were both higher in the samples with
higher indicative reflectance at that point. The resistivity of the GaN buffer layer was predominantly determined by an ∼0.25-μm-thick
layer near the GaN/Al2O3 interface. Atomic force microscope (AFM) and high-resolution x-ray diffraction (HRXRD) results showed that the samples with
higher indicative reflectance had smaller sized but higher density nuclei before the high-temperature GaN growth and lower
screw threading dislocation (TD) density in the initially grown GaN. The difference in the background electron concentration
and mobility of the interfacial layer was related to the relatively higher concentration of the O and Al diffused from Al2O3, which is also dependent on the size and density of the nuclei. These differences were found not to affect the structural
and electrical properties or the surface morphology of AlGaN/GaN high electron-mobility transistors (HEMTs, except for the
buffer conduction) when the GaN buffer is thick enough (e.g., ∼2.5 μm). 相似文献
8.
Guan-Ru Chen Hao-Hsiung Lin Jyh-Shyang Wang Ding-Kang Shih 《Journal of Electronic Materials》2003,32(4):244-248
Optical properties of InAs1−xNx/In0.53Ga0.47As (hereafter, abbreviated as InAsN/InGaAs) single quantum wells (SQWs) grown on InP substrates by gas source molecular-beam
epitaxy are studied using photoluminescence (PL) measurements. By comparing the low-temperature PL spectra of InAs/InGaAs
and InAsN/InGaAs SQWs, InAs and InAsN phases are found to coexist in the InAsN layer. Such serious alloy inhomogeneities result
in obvious exciton localization by potential irregularities. The blue shift of the PL peak after rapid thermal annealing (RTA)
is found to originate mainly from As-N interdiffusion inside the well layer. According to the temperature-dependent PL results,
uniformity of the InAsN layer can be effectively improved by RTA, and the exciton localization is, thus, relieved. Comparison
of luminescence quenching and excitation-power-dependent PL behavior between the QWs with and without nitrogen content suggests
that the quality of the QW is degraded by the introduction of nitrogen, and the degradation can only be partially recovered
by post-growth RTA. 相似文献
9.
Sridhar Govindaraju Jason M. Reifsnider Michael M. Oye Archie L. HolmesJr. 《Journal of Electronic Materials》2003,32(1):29-33
GaInNAs has received a great deal of attention among the scientific community, owing to its ability to be grown pseudomorphically
on GaAs substrates and, thus, to extend the possibility of using GaAs based materials for technologically important wavelengths
such as 1.3 μm. Annealing was found to be a very useful tool in improving the optical characteristics of as-grown GaInNAs
films. This work presents a systematic statistical analysis of two annealing parameters, time and temperature, for Ga0.8In0.2N0.01As0.99 quantum wells. Annealing, in general, has resulted in decreasing the emission wavelength by at most 0.08 μm, narrowing the
peaks by at most ∼25 meV and increasing the intensity by at most 90 times. However, from the statistical analysis, it is observed
that the temperature is the dominant factor among time and temperature in recovering the optical properties. 相似文献
10.
The role of the V-III ratio during growth on the optical and electrical properties of AlxGa1-x As laser material grown by metalorganic chemical vapor deposition has been investigated. Controlled studies involving more
than twenty growth runs show that this parameter has a profound influence on both device performance and reliability. 相似文献
11.
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
12.
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
13.
M. V. Chukichev B. M. Ataev V. V. Mamedov Ya. I. Alivov I. I. Khodos 《Semiconductors》2002,36(9):977-980
The cathodoluminescent properties of ZnO films in ZnO/GaN/α-Al2O3 and ZnO/α-Al2O3 heteroepitaxial structures grown by chemical vapor deposition in a low-pressure flowing-gas reactor were studied and compared. A superlinear dependence of the excitonic-band intensity in the cathodoluminescence spectrum of the ZnO/GaN/α-Al2O3 structures on the electron-beam current is ascertained, which indicates that the emission is stimulated for relatively low thresholds of the excitation intensity. It is shown that the ZnO films grown on the GaN substrates exhibit a much more effective cathodoluminescence compared to the cathodoluminescence in the films grown on α-Al2O3. It was observed that the luminescent properties of ZnO layers in the ZnO/GaN/α-Al2O3 structures subjected to long-term heat treatment at 750°C in an oxygen atmosphere exhibit a high thermal stability. 相似文献
14.
We report on the photoluminescent (PL) properties of ZnO thin films grown on SiO2/Si(100) substrates using low pressure metal-organic chemical vapor deposition. The growth temperature of the films was as
low as 400°C. From the PL spectra of the films at 10–300 K, strong PL peaks due to free and bound excitons were observed.
The origin of the near bandedge emission peaks was investigated measuring temperature-dependent PL spectra. In addition, the
Zn O films demonstrated a stimulated emission peak at room temperature. Upon illumination with an excitation density of 1
MW/cm2, a strong, sharp peak was observed at 3.181 eV. 相似文献
15.
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
16.
We report the growth by low-pressure metal-organic chemical vapor deposition, fabrication, and characterization of ten-layer In/sub 0.5/Ga/sub 0.5/As/GaAs quantum dot infrared photodetectors. Normal incidence photoresponse of the detector was obtained at 5.9 /spl mu/m. The 77-K peak responsivity was 5.6 mA/W with the detectivity D/sup */ of 1.2/spl times/10/sup 9/ cm/spl middot/Hz/sup 1/2//W at the bias of 0.4 V. 相似文献
17.
M. Takemi T. Kimura T. Miura K. Goto Y. Mihashi S. Takamiya 《Journal of Electronic Materials》1996,25(3):369-374
A comparative study has been carried out regarding selective embedding growth of InP by metalorganic chemical vapor deposition
(MOCVD) around dry-etched mesas, using two types of reactors: a conventional horizontal type and a highspeed rotating-susceptor
type. In the case of the conventional horizontal-type MOCVD, overgrowth on the mask was observed when the growth temperature
was low (600°C). On the other hand, an almost planar grown surface without such overgrowth was achieved by using the high-speed
rotating-susceptor MOCVD for a wide range of growth temperatures, especially even at a low growth temperature of 580°C. Regarding
the high-speed rotating-susceptor MOCVD, we have also investigated the effects of dopants on the growth behaviors and have
found a remarkable difference between n-type S-doped and p-type Zn-doped InP in the growth behaviors. The mechanism for suppressing
overgrowth in case of the high-speed rotating-susceptor MOCVD, as well as the cause for the different effects between the
dopants, are discussed. 相似文献
18.
Jae-Hyun Ryou Russell D. Dupuis C. V. Reddy Venkatesh Narayanamurti David T. Mathes Robert Hull Alexander Mintairov James L. Merz 《Journal of Electronic Materials》2001,30(5):471-476
We report the characteristics of InP self-assembled quantum dots embedded in In0.5Al0.5P on GaAs substrates grown by metalorganic chemical vapor deposition. The InP quantum dots show increased average dot sizes
and decreased dot densities, as the growth temperature increases from 475°C to 600°C with constant growth time. Above the
growth temperature of 600°C, however, dramatically smaller and densely distributed self-assembled InP quantum dots are formed.
The small InP quantum dots grown at 650°C are dislocation-free “coherent” regions with an average size of ∼20 nm (height)
and a density of ∼1.5 × 108 mm−2. These InP quantum dots have a broad range of luminescence corresponding to red or organge in the visible spectrum. 相似文献
19.
C. A. Tran J. T. Graham J. L. Brebner R. A. Masut 《Journal of Electronic Materials》1994,23(12):1291-1296
We present results of the growth of InAsxP1−x/InP strained heterostructures by low pressure metalorganic vapor phase epitaxy. A large incorporation of arsenic into the
InAsP ternary was observed using tertiarylbutylarsine as precursor. High resolution x-ray diffraction, photoluminescence,
and optical absorption measurements for InAsP/InP strained multiple quantum wells reveal that the InAsP/InP interface is very
sensitive to growth interruption. A systematic study of a growth in terruption sequence designed to improve the InAs/InP interface
was carried out. For nonoptimal growth interruption procedures a large density of interface states is created, probably as
a consequence of compositional modifications within the interface region. We find that the absorption spectrum may reveal
a significant density of interface states. Thus, photoluminescence on its own is insufficient to characterize the interface
roughness even for structures showing narrow low-temperature photoluminescence peaks. We also observe an enhancement of the
As content for structures grown on InP (001) relative to those simultaneously grown on InP(001) two degrees off toward [100],
which suggests that the composition of As in the ternary is limited by its surface diffusion. 相似文献
20.
S. -H. Park K. -B. Kim S. -Y. Seo S. -H. Kim S. -W. Han 《Journal of Electronic Materials》2006,35(8):1680-1684
We present the structural and optical properties of Zn1?xMgxO thin films studied using x-ray diffraction (XRD), extended x-ray absorption fine structure (EXAFS), and photoluminescence (PL) measurements. The Zn1?xMgxO films on sapphire [0001] substrates were fabricated with metal organic chemical vapor deposition (MOCVD). The XRD measurements showed that the Zn1?xMgxO films (x≤0.05) had a wurtzite structure without any MgO phase and were epitaxially grown along the c-axis of the Al2O3 substrate. The lattice constant of the Zn0.95Mg0.05O film shrank by 0.023 Å, compared with that of ZnO crystals. From the EXAFS measurements on the Zn1?xMgxO films at Zn K-edge, we found a substantial amount of distortion in the bond length of Zn-Zn pairs with a small amount of Mg substitution on the Zn site. The PL measurements showed a gradual increment of the main exciton transitions from 3.36 eV (x=0.0) to 3.57 eV (x=0.05) at 10 K. We also observed a strong deep-level emission near 2.3 eV from the specimen with x=0.05. 相似文献