共查询到20条相似文献,搜索用时 15 毫秒
1.
L. T. Romano B. S. Krusor R. Singh T. D. Moustakas 《Journal of Electronic Materials》1997,26(3):285-289
GaN films grown by electron-cyclotron resonance plasma-assisted molecular beam epitaxy were studied by transmission electron
microscopy and x-ray diffraction (XRD). Two sets of films were compared that were grown under identical conditions except
for the ratio of the Ga to N flux. Films with a 30% higher Ga to N ratio (A films) were found to contain inversion domains
(IDs). No IDs were found in films grown with a lower Ga to N ratio (B films), but instead the zinc-blende GaN was found near
the film substrate interface. A narrower XRD rocking curve width along the (0002) direction and a broader rocking curve width
along the asymmetric (1102) axis were found for A films compared to B films. 相似文献
2.
We study the plasma-assisted molecular beam epitaxy of cubic GaN on GaAs(OOl) substrates by means ofin-situ reflection high-energy electron diffraction. The epilayers are characterized by x-ray diffraction, photoluminescence, and
Hall measurements, and it is found that the overall best films are grown under a N/Ga ratio close to one. For anin-situ determination of the N/Ga ratio, the growth kinetics is studied via surface reconstruction transitions. The effective N flux
giving rise to growth is measured using the transient behavior of the half-order diffraction streak intensity for various
plasma operating conditions. 相似文献
3.
报道了InAs/GaSb超晶格中波材料的分子束外廷生长技术研究.通过改变GaSb衬底上分子束外延InAs/GaSb超晶格材料的衬底温度,以及界面的优化等,改善超晶格材料的表面形貌和晶格失配,获得了晶格失配△a/a=1.5×10-4,原子级平整表面的InAs/GaSb超晶格材料,材料77 K截止波长为4.87 μm. 相似文献
4.
We have studied the properties of molecular beam epitaxially (MBE)-grown Erdoped III-V semiconductors for optoelectronic applications.
Optically excited Er3+ in insulating materials exhibits optical emission chiefly around 1.54 μm, in the range of minimum loss in silica fiber. It
was thought, therefore, that an electrically pumped Er-doped semiconductor laser would find great applicability in fiber-optic
communication systems. Exhaustive photoluminescence (PL) characterization was conducted on several of As-based III-V semiconductors
doped with Er, on bulk as well as quantum-well structures. We did not observe any Errelated PL emission at 1.54 μm for any
of the materials/structures studied, a phenomenon which renders impractical the realization of an Er-doped III-V semiconductor
laser. Deep level transient spectroscopy studies were performed on GaAs and AlGaAs co-doped with Er and Si to investigate
the presence of any Er-related deep levels. The lack of band-edge luminescence in the GaAs:Er films led us to perform carrier-lifetime
measurements by electro-optic sampling of photoconductive transients generated in these films. We discovered lifetimes in
the picosecond regime, tunable by varying the Er concentration in the films. We also found the films to be highly resistive,
the resistivity increasing with increasing Er-concentration. Intensive structural characterization (double-crys-tal x-ray
and transmission electron microscopy) performed by us on GaAs:Er epilayers indicates the presence of high-density nanometer-sized
ErAs precipitates in MBE-grown GaAs:Er. These metallic nanoprecipitates probably form internal Schottky barriers within the
GaAs matrix, which give rise to Shockley-Read-Hall recombination centers, thus accounting for both the high resistivities
and the ultrashort carrier lifetimes. Optoelectronic devices fabricated included novel tunable (in terms of speed and responsivity)
high-speed metal-semiconductor-metal (MSM) photodiodes made with GaAs:Er. Pseudomorphic AlGaAs/ InGaAs modulation doped field
effect transistors (MODFETs) (for high-speed MSM-FET monolithically integrated optical photoreceivers) were also fabricated
using a GaAs:Er buffer layer which substantially reduced backgating effects in these devices. 相似文献
5.
Jun Fang Fan Zhang Wenxian Yang Aiqin Tian Jianping Liu Shulong Lu Hui Yang 《半导体学报》2024,45(1):012503-1-012503-7
The InGaN films and GaN/InGaN/GaN tunnel junctions (TJs) were grown on GaN templates with plasma-assisted molecular beam epitaxy. As the In content increases, the quality of InGaN films grown on GaN templates decreases and the surface roughness of the samples increases. V-pits and trench defects were not found in the AFM images. p++-GaN/InGaN/n++-GaN TJs were investigated for various In content, InGaN thicknesses and doping concentration in the InGaN insert layer. The InGaN insert layer can promote good interband tunneling in GaN/InGaN/GaN TJ and significantly reduce operating voltage when doping is sufficiently high. The current density increases with increasing In content for the 3 nm InGaN insert layer, which is achieved by reducing the depletion zone width and the height of the potential barrier. At a forward current density of 500 A/cm2, the measured voltage was 4.31 V and the differential resistance was measured to be 3.75 × 10−3 Ω·cm2 for the device with a 3 nm p++-In0.35Ga0.65N insert layer. When the thickness of the In0.35Ga0.65N layer is closer to the “balanced” thickness, the TJ current density is higher. If the thickness is too high or too low, the width of the depletion zone will increase and the current density will decrease. The undoped InGaN layer has a better performance than n-type doping in the TJ. Polarization-engineered tunnel junctions can enhance the functionality and performance of electronic and optoelectronic devices. 相似文献
6.
The growth of InN on {0001} ZnO substrates by radio-frequency, plasma-assisted, molecular-beam epitaxy (RF-MBE) has been experimentally
investigated. The reflection high-energy electron diffraction (RHEED) pattern quickly recovered to a 1×1 streak pattern as
the InN growth was started on nitridated ZnO substrates, whereas the RHEED pattern of the ZnO substrate was spotty because
of plasma damage induced by nitridation. The full width at half maximum (FWHM) of the (0002) InN rocking curve was estimated
to be around 150 arcsec from x-ray diffraction (XRD). Furthermore, we observed a remarkable feature from our experiments;
namely, the crystal quality of InN does not seem to depend on the surface polarity of the ZnO substrate, while it is well
known that InN growth on GaN has strong polarity dependence. To investigate this tendency, we have also investigated the surface
stability of adatoms, In and N, on Zn- and O-face ZnO surfaces using a first-principles technique. From the theoretical study,
N adsorption is more stable on ZnO surfaces of both polarities compared with In adsorption. Accordingly, the preferential
initiation by N adatoms onto both ZnO surfaces can explain the unique style of InN growth on ZnO substrates. 相似文献
7.
David Pritchett Walter Henderson Shawn D. Burnham W. Alan Doolittle 《Journal of Electronic Materials》2006,35(4):562-567
The surface reaction byproducts during the growth of GaN films via metal organic molecular beam epitaxy (MOMBE) were investigated
as a means to optimize material properties. Ethylene and ethane were identified as the dominant surface reaction hydrocarbon
byproducts, averaging 27.63% and 7.15% of the total gas content present during growth. Intense ultraviolet (UV) photoexcitation
during growth was found to significantly increase the abundance of ethylene and ethane while reducing the presence of H2 and N2. At 920°C, UV excitation was shown to enhance growth rate and crystalline quality while reducing carbon incorporation. Over
a limited growth condition range, a 4.5×1019−3.4×1020 cm−3 variation in carbon incorporation was achieved at constant high vacuum. Coupled with growth rate gains, UV excitation yielded
films with ∼58% less integrated carbon content. Structural material property variations are reported for various ammonia flows
and growth temperatures. The results suggest that high carbon incorporation can be achieved and regulated during MOMBE growth
and that in-situ optimization through hydrocarbon analysis may provide further enhancement in the allowable carbon concentration
range. 相似文献
8.
Brett Z. Nosho John A. Roth John E. Jensen Le Pham 《Journal of Electronic Materials》2005,34(6):779-785
The fabrication of high-quality focal plane arrays from HgCdTe layers grown by molecular beam epitaxy (MBE) requires a high
degree of lateral uniformity in material properties such as the alloy composition, doping concentration, and defect density.
While it is well known that MBE source flux nonuniformity can lead to radial compositional variation for rotating substrates,
we have also found that composition can be affected significantly by lateral variations in substrate temperature during growth.
In diagnostic experiments, we systematically varied the substrate temperature during MBE and quantified the dependence of
HgCdTe alloy composition on substrate temperature. Based on these results, we developed a methodology to quickly and nondestructively
characterize MBE-grown layers using postgrowth spatial mapping of the cutoff wavelength from the Fourier transform infrared
(FTIR) transmission at 300 K, and we were able to obtain a quantitative relationship between the measured spatial variations
in cutoff and the substrate temperature lateral distribution during growth. We refined this methodology by more directly inferring
the substrate temperature distribution from secondary ion mass spectroscopy (SIMS) measurements of the As concentration across
a wafer, using the fact that the As incorporation rate in MBE-grown p-type layers is highly sensitive to substrate temperature.
Combining this multiple-point SIMS analysis with FTIR spatial mapping, we demonstrate how the relative contributions from
flux nonuniformity and temperature variations on the lateral composition uniformity can be separated. This capability to accurately
map the lateral variations in the substrate temperature has been valuable in optimizing the mounting and bonding of large
substrates for MBE growth, and can also be valuable for other aspects of MBE process development. 相似文献
9.
M. Zandian J. M. Arias J. Bajaj J. G. Pasko L. O. Bubulac R. E. Dewames 《Journal of Electronic Materials》1995,24(9):1207-1210
Characterization of defects in Hg1−xCdxTe compound semiconductor is essential to reduce intrinsic and the growth-induced extended defects which adversely affect
the performance of devices fabricated in this material system. It is shown here that particulates at the substrate surface
act as sites where void defects nucleate during Hg1−xCdxTe epitaxial growth by molecular beam epitaxy. In this study, we have investigated the effect of substrate surface preparation
on formation of void defects and established a one-to-one correlation. A wafer cleaning procedure was developed to reduce
the density of such defects to values below 200 cm−2. Focal plane arrays fabricated on low void density materials grown using this new substrate etching and cleaning procedure
were found to have pixel operability above 98.0%. 相似文献
10.
ZnO thin films were grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy (MBE). The crystalline
properties of the layers as measured by x-ray diffraction were found to improve with lower growth temperatures, where the
full-width at half-maximum (FWHM) of the x-ray rocking curves was shown to be in the range of 100 to 1,100 arcsec. The electronic
properties were found to improve for higher growth temperatures, with n-type carrier concentration and electron mobility in
the range of 1×1017 −5×1018 cm−3 and 80–36 cm2/Vs, respectively. Photoluminescence (PL) measurements indicated that growth at higher temperatures provided superior band
edge radiative emission, while growth at lower temperatures resulted in significant deep level radiative emission centered
at 2.35 eV. Photoconductive decay measurements exhibit a slow decay indicating the presence of hole traps, where Zn vacancies
are believed to be the source of both the slow decay and the deep level emission observed in PL spectra. 相似文献
11.
R. Held D. E. Crawford A. M. Johnston A. M. Dabiran P. I. Cohen 《Journal of Electronic Materials》1997,26(3):272-280
Methods to determine GaN surface temperature, surface composition, and growth rates using in situ desorption mass spectroseopy (DMS) and reflection high energy electron diffraction (RHEED) are demonstrated for molecular
beam epitaxial growth of GaN using NH3. Using these methods, the GaN surface temperature, Ts, and GaN growth rates as a function of Ts, Ga flux, and NH3 flux were obtained. Surface temperatures were determined from DMS and RHEED measurements of the temperature at which Ga condenses
on GaN. NH3-limited and Ga-limited growth regimes are identified and the transition between these regimes is shown to be abrupt. NH3-limited samples have a weakly reconstructed (2 × 2) RHEED pattern, while Ga-limited samples reveal a transmission pattern.
Atomic force microscopy showed that NH3-limited samples exhibit atomic steps while Ga-limited samples exhibit faceting. 相似文献
12.
C. D. Lee V. Ramachandran A. Sagar R. M. Feenstra D. W. Greve W. L. Sarney L. Salamanca-Riba D. C. Look Song Bai W. J. Choyke R. P. Devaty 《Journal of Electronic Materials》2001,30(3):162-169
The structural, electrical, and optical properties of GaN grown on 6H-SiC(0001) substrates by molecular beam epitaxy are studied.
Suitable substrate preparation and growth conditions are found to greatly improve the structural quality of the films. Threading
dislocation densities of about 3×109 cm−2 for edge dislocations and <1×106 cm−2 for screw dislocations are achieved in GaN films of 0.8 μm thickness. Mechanisms of dislocation generation and annihilation
are discussed. Increasing the Ga to N flux ratio used during growth is found to improve the surface morphology. An unintentional
electron concentration in the films of about 5×1017 cm−3 is observed, and is attributed to excess Si in the films due to a Si-cleaning step used in the substrate preparation. Results
from optical characterization are correlated with the structural and electronic studies. 相似文献
13.
Lijie Zhao J. S. Speck R. Rajavel J. Jensen D. Leonard T. Strand W. Hamilton 《Journal of Electronic Materials》2000,29(6):732-735
Transmission electron microscopy (TEM) was used to evaluate the microstructure of molecular beam epitaxy (MBE) grown (211)B
oriented HgCdTe films. TEM analysis of in-situ doped p-on-n and n-p-n device structures will be presented. Under fully optimized
growth conditions the substrate-epilayer interface is free of threading dislocations and twins, and a high degree of structural
integrity is retained throughout the entire device structure. However, under non-optimal growth conditions that employ high
Hg/Te flux ratios, twins can be generated in the p-type layer of p-on-n device structure, resulting in roughness and facetting
of the film surface. We propose a mechanism for twin formation that is associated with surface facetting. TEM evaluation of
voids, threading dislocations and Te-precipitates in HgCdTe films are also discussed. 相似文献
14.
GaN p-i-n photodetectors grown on sapphire by reactive molecular beam epitaxy have been characterized by measurements of room-temperature
current-voltage (I-V), temperature-dependent capacitance (C-V-T), and deep level transient spectroscopy (DLTS) under both
majority and minority carrier injection. Due to what we believe to be threading dislocations, the reverse I-V curves of p-i-n
photodetectors show typical electric-field enhanced soft breakdown characteristics. A carrier freeze-out due to the de-ionization
of Mg-related deep acceptors has been found by C-V-T measurements. Three electron traps, B (0.61 eV), D (0.23 eV), and E1 (0.25 eV) and one hole trap, H3 (0.79 eV) have been revealed by DLTS measurements. The photodetectors with lower leakage currents usually show higher responsivity
and lower trap densities of D and E1. 相似文献
15.
S. M. Donovan J. D. Mackenzie C. R. Abernathy S. J. Pearton P. C. Chow J. Van Hove 《Journal of Electronic Materials》1997,26(11):1292-1296
The effects of growth temperature and nitrogen plasma biasing on the electrical and structural properties of InN grown using
electron cyclotron resonance metalorganic molecular beam epitaxy (ECR MOMBE) have been investigated. These results are compared
to those found from InN grown using a higher energy radio frequency (rf) plasma source (rf MOMBE). By varying the bias of
the nitrogen plasma or the growth temperature, it is possible to achieve smooth surface morphologies. However, biasing can
also be used to increase the mobility by a factor of two while the growth temperature has only a small effect. By contrast,
use of an rf plasma improves mobility by nearly a factor of ten. None of the growth conditions investigated were found to
significantly alter the electron concentration, which was measured to be 1−5 × 1020 cm−3. 相似文献
16.
S. F. Yoon Y. B. Miao K. Radhakrishnan S. Swaminathan 《Journal of Electronic Materials》1996,25(9):1458-1462
Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different silicon doping levels is carried out. The doped
samples show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping
levels due to a possible reduction in the donor binding energy. There is a reduction in both the AlAs-like and InAs-like longitudinal-optic
(LO) phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased. The PL intensity also
showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous
materials. 相似文献
17.
R. Jothilingam M. W. Koch J. B. Posthill G. W. Wicks 《Journal of Electronic Materials》2001,30(7):821-824
It is observed that GaN layers grown on silicon substrates often crack. The crack characteristics in hexagonal GaN films on
Si(111) has been characterized using scanning electron microscopy and Nomarski optical microscopy. The effects of growth temperature,
layer thickness, and V/III ratios on the cracking have been analyzed. The critical thickness for crack initiation was estimated
using a simple theoretical model and is shown to have good agreement with experimental results. Crack-free GaN on Si(111)
of thicknesses greater than one micron is possible by using low growth temperatures. 相似文献
18.
Yoshitaka Okada Shigeru Ohta Akio Kawabata Hirofumi Shimomura Mitsuo Kawabe 《Journal of Electronic Materials》1994,23(3):331-335
Preliminary experimental results and analysis of photoluminescence (PL) measurements performed on GaAs heteroepitaxial films,
which have been grown on Si(100) substrates by atomic hydrogen-assisted low-temperature molecular beam epitaxy technique have
been presented and discussed. The results have also been compared with those obtained for GaAs homoepitaxial films. Furthermore,
minority carrier lifetimes in n-GaAs on Si have been characterized by the PL decay method and an average lifetime of as high
as 8.0 ns has been successfully obtained, which is the highest value ever reported to date. 相似文献
19.
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
20.
Dual-band infrared detectors made on high-quality HgCdTe epilayers grown by molecular beam epitaxy on CdZnTe or CdTe/Ge substrates 总被引:2,自引:0,他引:2
P. Ballet F. Noël F. Pottier S. Plissard J. P. Zanatta J. Baylet O. Gravrand E. De Borniol S. Martin P. Castelein J. P. Chamonal A. Million G. Destefanis 《Journal of Electronic Materials》2004,33(6):667-672
In this paper, we present all the successive steps for realizing dual-band infrared detectors operating in the mid-wavelength
infrared (MWIR) band. High crystalline quality HgCdTe multilayer stacks have been grown by molecular beam epitaxy (MBE) on
CdZnTe and CdTe/Ge substrates. Material characterization in the light of high-resolution x-ray diffraction (HRXRD) results
and dislocation density measurements are exposed in detail. These characterizations show some striking differences between
structures grown on the two kinds of substrates. Device processing and readout circuit for 128×128 focal-plane array (FPA)
fabrication are described. The electro-optical characteristics of the devices show that devices grown on Ge match those grown
on CdZnTe substrates in terms of responsivity, noise measurements, and operability. 相似文献