共查询到10条相似文献,搜索用时 140 毫秒
1.
Dapeng Xu Hui Yang J. B. Li S. F. Li Y. T. Wang D. G. Zhao R. H. Wu 《Journal of Electronic Materials》2000,29(2):177-182
We have investigated the growth of GaN buffers by metalorganic chemical vapor deposition (MOCVD) on GaAs (100) substrates.
Atomic force microscope (AFM) and reflection high-energy electron diffraction (RHEED) were employed to study the dependence
of the nucleation on the growth temperature, growth rate, annealing effect, and growth time. A two-step growth sequence must
be used to optimize and control the nucleation and the subsequent growth independently. The size and distribution of islands
and the thickness of buffer layers have a crucial role on the quality of GaN layers. Based on the experimental results, a
model was given to interpret the formation of hexagonal-phase GaN in the cubic-phase GaN layers. Using an optimum buffer layer,
the strong near-band emission of cubic GaN with full-width at half maximum (FWHM) value as small as 5.6 nm was observed at
room temperature. The background carrier concentration was estimated to be in the range of 1013 ∼ 1014 cm−3. 相似文献
2.
Tri-Buffer Process: A New Approach to Obtain High-Quality ZnO Epitaxial Films on Sapphire Substrates
Z. X. Mei X. L. Du Y. Wang M. J. Ying Z. Q. Zeng H. T. Yuan J. F. Jia Q. K. Xue Z. Zhang 《Journal of Electronic Materials》2007,36(4):452-456
A tri-buffer method was applied to achieve layer-by-layer growth of high-quality ZnO films on sapphire (0001) substrates by
rf plasma-assisted molecular beam epitaxy (MBE). After sufficient nitridation of the substrate, MgO and ZnO buffer layers
were subsequently deposited on the resulting AlN layer. An atomically smooth ZnO surface with a roughness less than 1 nm in
a 10 μm × 10 μm scanned area was obtained with this method. The crystal quality was also improved, as characterized by reflection high-energy
electron diffraction (RHEED), x-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The
results indicate that the tri-buffer process could reduce the large lattice mismatch between ZnO and nitrided sapphire and
facilitate the two-dimensional (2-D) growth of the ZnO epilayer. A model is proposed to understand the observations. 相似文献
3.
Hyonju Kim Fredrik J. Fälth Thorvald G. Andersson 《Journal of Electronic Materials》2001,30(10):1343-1347
We have investigated systematically the effects of growth parameters upon the unintentional incorporation of B, As, and O
impurities in GaN grown by molecular beam epitaxy with an RF-plasma activated nitrogen source. The prepared samples were analyzed
using secondary ion mass spectrometry to determine the absolute concentration of the impurities. The boron background concentration
in the unintentionally doped GaN was found to strongly correlate with the nitrogen plasma power used during the growth, indicating
a decomposition of the pBN crucible in the plasma source. Due to previous GaAs growth in the same chamber, a considerably
large amount of As contamination (≈3×1018 at/cm3) was also observed in the grown layer. The presence of Al in GaN is found to facilitate the incorporation of oxygen impurities
in the layer. We determined an empirical formula, Co
t/Co
b 3.8×(CAl/CAl)0.27, representing the correlation between O concentration and Al mole fraction (%) in the small range of Al content, 0.03≈1%,
in the layer. The residual oxygen level was substantially reduced from 3.4×1019 to mid-1018 at/cm3 in the GaN layer when the buffer layer structure was changed from low temperature grown GaN single buffer to GaN/AlN double
buffer layer. We ascribe this significantly lowered oxygen impurity level to improved crystalline quality of the layer due
to the double buffer layer structure. 相似文献
4.
《Materials Science in Semiconductor Processing》2009,12(6):233-237
ZnO thin films without and with a homo-buffer layer have been prepared on Si(1 1 1) substrates by pulsed laser deposition (PLD) under various conditions. Photoluminescence (PL) measurement indicates that the optical quality of ZnO thin film is dramatically improved by introducing oxygen into the growth chamber. The sample deposited at 60 Pa possesses the best optical properties among the oxygen pressure range studied. X-ray diffraction (XRD) results show that the films directly deposited on Si are of polycrystalline ZnO structures. A low-temperature (500 °C) deposited ZnO buffer layer was used to enhance the crystal quality of the ZnO film. Compared to the film without the buffer layer, the film with the buffer layer exhibits aligned spotty reflection high-energy electron diffraction (RHEED) pattern and stronger near-band-edge emission (NBE) with a smaller full-width at half-maximum (FWHM) of 98 meV. The structural properties of ZnO buffer layers grown at different temperatures were investigated by RHEED patterns. It is suggested that the present characteristics of the ZnO epilayer may be raised further by elevating the growth temperature of buffer layer to 600 °C. 相似文献
5.
We have investigated effects of annealing of MgO buffer layer on structural quality of ZnO layers grown by plasma assisted molecular beam epitaxy on c-sapphire. ZnO layers were characterized by atomic force microscopy, high resolution X-ray diffraction (HRXRD) and cross sectional transmission electron microscopy (TEM). AFM images show that annealing of a low temperature (LT)-MgO buffer at high temperatures enhanced the surface migration of adatoms, leading to the formation of larger terraces and smoother surface morphology, as indicated by the reduction of rms values of roughness from 0.6 to 0.3 nm. HRXRD and TEM experiments reveal that the dislocation density of ZnO layers is reduced from 5.3×109 to 1.9×109 cm−2 by annealing a LT-MgO buffer. All of those features indicate the structural quality of ZnO layers was improved by annealing a LT-MgO buffer layer. 相似文献
6.
S. K. Davidsson M. Gurusinghe T. G. Andersson H. Zirath 《Journal of Electronic Materials》2004,33(5):440-444
We have studied the influence of Al content, AlGaN layer thickness, and unintentional background doping by oxygen on the two-dimensional electron gas (2DEG) density in AlGaN/GaN heterostructures. Hall measurements were made on samples grown with molecular beam epitaxy. The 2DEG densities in the range 2–3×1013 cm?2 were measured. A one-dimensional Schrödinger-Poisson model was used to describe the heterostructure. The calculations gave two-dimensional electron densities in accordance with measured values. The electron density is very sensitive to the Al concentration in the AlGaN layer, whereas the sensitivity to layer thickness is small. Our simulations also showed that the two-dimensional concentration increased 50% when the free-carrier concentration changed from 1015 cm?3 to 1018 cm?3. The relation between donor concentration and free-carrier concentration was found to agree when using oxygen ionization energy as a parameter. 相似文献
7.
The deposition of a multilayer buffer layer that includes a high-temperature AlN layer grown at a temperature above 1100°C has made it possible to reduce the dislocation density in a GaN layer by 1.5?C2 orders of magnitude to values in the range from 9 × 108 to 1 × 109 cm?2, compared with the case of growth on a thin low-temperature AlN nucleation layer. The decrease in the dislocation density causes a substantial increase in the electron mobility in the GaN layers to 600?C650 cm2 V?1 s?1, which is in agreement with the results of calculations and is indicative of the high crystalline perfection of the layers. 相似文献
8.
SiC semiconductor-on-insulator (SOI) structures have been investigated as substrates for the growth of GaN films. The SiC
SOI was obtained through the conversion of Si SOI wafers by reaction with propane and H2. (111) SiC SOI have been produced by this carbonization process at temperatures ranging from 1200 to 1300°C. X-ray diffraction
(XRD) and infrared spectroscopy (FTIR) are used to chart the conversion of the Si layer to SiC. Under our conditions, growth
time of 3 min at 1250°C is sufficient to completely convert a 1000? layer. XRD of the SiC SOI reveals a single SiC peak at
2θ = 35.7° corresponding to the (111) reflection, with a corrected full width at half-maximum (FWHM) of ~590±90 arc-sec. Infrared
spectroscopy of SiC SOI structures obtained under optimum carboniza-tion conditions exhibited a sharp absorption peak produced
by the Si-C bond at 795 cm−1, with FWHM of ∼ 20–25 cm−1. Metalorganic CVD growth of GaN on the (111) SiC SOI was carried out with trimethylgallium and NH3. The growth of a thin (≤200?), low temperature (500°C) GaN buffer layer was followed by the growth of a thick (∼2 μm) layer
at 1050°C. Optimum surface morphology was obtained for zero buffer layer. XRD indicates highly oriented hexagonal GaN, with
FWHM of the (0002) peak of ~360±90 arc-sec. Under high power excitation, the 300°K photoluminescence (PL) spectrum of GaN
films exhibits a strong near band-edge peak (at λp~371 nm, with FWHM = 100–150 meV) and very weak yellow emission. Under low power excitation, the 370 nm PL emission from the
GaN/SiC SOI structure increases rapidly with SiC carbonization temperature, while the yellow band (∼550–620 nm) correspondingly
decreases. 相似文献
9.
ZnO and related materials: Plasma-Assisted molecular beam epitaxial growth, characterization and application 总被引:4,自引:0,他引:4
S. K. Hong Y. Chen H. J. Ko H. Wenisch T. Hanada T. Yao 《Journal of Electronic Materials》2001,30(6):647-658
This paper will address features of plasma-assisted molecular beam epitaxial growth of ZnO and related materials and their
characteristics. Two-dimensional, layer-by-layer growth is achieved both on c-plane sampphire by employing MgO buffer layer
growth and on (0001) GaN/Al2O3 template by predepositing a low-temperature buffer layer followed by high-temperature annealing. Such two-dimensional growth
results in the growth of high-quality heteroepitaxial ZnO epilayers. Biexciton emission is obtained from such high quality
epilayers The polarity of heteroepitaxial ZnO epilayers is controlled by engineering the heterointerfaces. We achieved selective
growth of Zn-polar and O-polar ZnO heteroepitaxial layers. The origin of different polarities can be successfully explained
by an interface bonding sequence model. N-type conductivity in Gadoped ZnO epilayers is successfully controlled. High conductivity,
enough to be applicable to devices, is achieved. MgxZn1-xO/ZnO heterostructures are grown and emission from a ZnO quantum well is observed. Mg incorporation in a MgZnO alloy is determined
by in-situ reflection high-energy electron diffraction intensity oscillations, which enables precise control of the composition.
Homoepitaxy on commericial ZnO substrates has been examined. Reflection high-energy electron diffraction intensity oscillations
during homoepitaxy growth are observed. 相似文献
10.
M. A. L. Johnson Shizuo Fujita W. H. Rowland W. C. Hughes Y. W. He N. A. El-Masry J. W. Cook J. F. Schetzina J. Ren J. A. Edmond 《Journal of Electronic Materials》1996,25(5):793-797
The growth of GaN and AlGaN by molecular beam epitaxy (MBE) has been studied using GaN/SiC substrates. The GaN/SiC substrates
consisted of ∼3 μm thick GaN buffer layers grown on 6H-SiC wafers by metalorganic vapor phase epitaxy (MOVPE) at Crée Research,
Inc. The MBE-grown GaN films exhibit excellent structural and optical properties—comparable to the best GaN grown by MOVPE.
AlxGa1−xN films (x ∼ 0.06-0.08) and AlxGa1−xN/GaN multi-quantum-well structures which display good optical properties were also grown by MBE on GaN/SiC substrates. 相似文献