共查询到20条相似文献,搜索用时 359 毫秒
1.
K. Capuder P. E. Norris H. Shen Z. Hang F. H. Pollak 《Journal of Electronic Materials》1990,19(4):295-298
The contactless electromodulation method of photoreflectance has been successfully applied as an in-situ sensor of the OMVPE
process. The direct band gap,E
0, of GaAs and AIGaAs has been measured, in-situ, under OMVPE growth conditions. To the best of our knowledge, this is the
first report of an in-situ photoreflectance measurement of III-V materials properties in an OMVPE system. This is significant
in that it illustrates the potential for the application of photoreflectance as an in-situ process monitor, analogous to the
use of RHEED measurements in MBE. The GaAs substrate temperature of 650°, as measured by an optical pyrometer, corresponds
to the temperature derived using the Varshni equation and published Varshni coefficients to within the error of the published
data. 相似文献
2.
W. T. Tsang 《Journal of Electronic Materials》1986,15(4):235-245
The growth kinetics of chemical beam epitaxy (CBE) were investigated with the growth of GaAs, AIGaAs, InP, and InGaAs. Results
obtained with epilayers grown by using trimethylarsine (TMAs) and triethylphosphine (TEP) instead of arsine (AsH3) and phosphine
(PH3) were reviewed with some additional results. The CBE grown epilayers have similar optical quality to those grown by molecular
beam epitaxy (MBE). Superlattices of GaAs/AlGaAs with abrupt interfaces have been prepared. Since trimethylindium (TMIn) and
triethylgallium (TEGa) used in the growth of InGaAs emerged as a single mixed beam, spatial composition uniformity was automatically
achieved without the need of substrate rotation in the InGaAs epilayers grown. Lattice-mismatch Δα/α< 1 x 10-3 have been reproducibly obtained. For epilayers grown with high purity TMAs source, room-temperature electron mobility as
high as 9000 cm2/V sec and concentrations of ˜7 x 1015 cm-3 were produced. In general, the electron mobilities were as good as those obtained from low-pressure metalorganic chemical
vapor deposition. (MO-CVD). Unlike MBE, since the In and Ga were derived by the pyrolysis of TMIn and TEGa molecules at the
heated substrate surface, respectively, oval defects observed in MBE grown epilayers due to Ga splitting from Ga melt were
not present in CBE grown epilayers. This is important for integrated circuit applications. Unlike MO-CVD, the beam nature
of CBE allows for selective area growth of epilayers with well-defined smooth edges using mask shadowing techniques. Typically,
growth rates of 2-5μm/h for InP, 2-6μm/h for GaAs and AIGaAs, and 2-5μm/h for InGaAs were used. 相似文献
3.
M. J. Bevan L. A. Almeida W. M. Duncan H. D. Shih 《Journal of Electronic Materials》1997,26(6):502-506
A systematic study of the effect of measurement perturbation on in situ monitoring of the composition of molecular beam epitaxially (MBE) grown Hg1−xCdxTe using spectroscopic ellipsometry was carried out. Of the five variables investigated, which included angle of incidence,
wavelength of the light beam, modulator rotation, analyzer rotation, and modulator amplitude, the angle of incidence and the
modulator rotation had the strongest effect on the in situ Hg1−xCdxTe composition monitoring process. A wobble-free sample manipulator was installed to reduce the impact of these two variables.
With these improvements, the spectroscopic ellipsometer is now routinely used to monitor Hg
1−xCdxTe compositions during MBE growth of heterostructures and is a useful tool in diagnosing growth-related problems. Examples
are included for both application areas, that include the control of the interface between Hg1−xCdxTe layers of different compositions, i.e. device engineering. 相似文献
4.
S. Velicu C.H. Grein J. Zhao Y. Chang S.-Y. An A. Yadav K. Pipe W. Clark 《Journal of Electronic Materials》2008,37(9):1504-1508
We present a study on the thermoelectric properties of n-type Hg0.75Cd0.25 Te/Hg0.7Cd0.3Te superlattices (SLs). This material system was chosen because HgCdTe is the primary material used in high-performance infrared
imaging applications. HgCdTe-based devices can be directly grown on Hg1−x
Cd
x
Te/Hg1−y
Cd
y
Te SL coolers using advanced growth methods such as molecular-beam epitaxy (MBE), making the monolithic integration of infrared
sensors and thermoelectric elements possible. Also, the thermoelectric figure of merit ZT for Hg0.75Cd0.25Te/Hg0.7Cd0.3Te SLs is predicted to reach values of 2.09, more than two times greater than that achieved in the best thermoelectric devices
based on bulk Bi2Te3. This large ZT is due to the unique and superior electrical and thermal properties of the HgCdTe system, which has not yet been experimentally
explored in any great depth as a thermoelectric material. We used a Riber 32P MBE system equipped with a Hg valved cell, reflection
high-energy electron diffraction, infrared pyrometer and in situ spectroscopic ellipsometry to grow the thermoelectric structures. MBE was chosen as a growth technique since it allows for
the lowest growth temperature compared with other methods, which limits interdiffusion at the interfaces, thereby allowing
for a precise control over electrical and thermal properties. Thermal devices were fabricated using standard photolithography
and etching techniques. Thermal properties were evaluated using a differential technique. A thermal conductivity of 0.82 ± 0.07 W/m K
and a Seebeck coefficient of 811 ± 150 μV/K were measured. Using a measured value of 0.017 Ω cm for the resistivity, an upper bound ZT of 1.4 is estimated.
An erratum to this article can be found at 相似文献
5.
Marko J. Tadjer Travis J. Anderson Karl D. Hobart Michael A. Mastro Jennifer K. Hite Joshua D. Caldwell Yoosuf N. Picard Fritz J. Kub Charles R. EddyJr. 《Journal of Electronic Materials》2010,39(11):2452-2458
A comparative study of AlGaN/GaN high-electron-mobility transistor (HEMT) surface passivation using ex situ and in situ deposited SiN
x
is presented. Performing ex situ SiN
x
passivation increased the reverse gate leakage and off-state channel leakage by about three orders of magnitude. The in situ SiN
x
layer was characterized using transmission electron microscopy (TEM) and capacitance–voltage (CV) measurements. Photoluminescence
(PL) spectra indicated a reduction of nonradiative recombination centers in in situ SiN
x
-passivated samples, indicating improved crystal quality. CV measurements indicated a reduction of surface state density as
well, and thus better overall passivation using in situ SiN
x
. Electroluminescence (EL) images of the channel regions in AlGaN/GaN HEMT devices operating in forward blocking mode with
up to 400 V drain bias demonstrated reduced channel emission profiles of in situ-passivated devices. Compared with a nonpassivated reference sample, the reduced EL emission profiles correlated with a reduced
channel temperature on ex situ SiN
x
-passivated devices. 相似文献
6.
M. J. Bevan W. M. Duncan G. H. Westphal H. D. Shih 《Journal of Electronic Materials》1996,25(8):1371-1374
The current status of the implementation and refinement of two wafer state sensors forin situ monitoring and control during molecular beam epitaxial (MBE) growth of Hg1−xCdxTe will be reported. First a rapid scan spectral ellipsometer has been developed and employed for precisely measuring compositions
of Hg1−xCdxTe alloys during growth. MBE films in the composition range x = 0.20 to 0.30 have been grown andin situ spectra taken at the growth temperature (180°C) and at room temperature. The MBE films were treated as single layers without
the need to invoke any surface film (due to surface roughness, oxide, or of any different composition) as required for exsitu data. The least squares fit over the whole spectral range was used as a measure of the precision. The film composition was
also determinedex situ by wavelength dispersive analysis of x-rays and by Fourier transform infrared (FTIR) spectrometry after verifying that there
was no lateral variation. A precision of better than ±0.0015 has so far been demonstrated usingin situ spectral ellipsometry for Cd composition or CdTe mole fraction, x, measurements. This compares with ±0.003 for single wavelength
ellipsometry. The composition of Hg1−xCdxTe films were also monitored during growth. A spectral pyrometer based on a FTIR spectrometer has also been developed for
substrate temperature measurements during growth. The spectral pyrometer measures both the emission and reflectance to give
the emissivity of a growing sample over a range of wavelengths spanning the peak of the grey body emission. From the reflectivity
measurements, the thickness (in excess of 1 μm) of the growing film is also determined from the interference fringes. The
spectral ellipsometer is only capable of measuring thicknesses up to C.a 5000°A (i.e. optically thin). Excellent agreement
is obtained between thein situ (at growth temperature) andex situ (at room temperature) thickness measurements. The small discrepancy can be explained by the refractive index of Hg1−xCdxTe being 5% higher at the growth temperature than at room temperature. The combination ofin situ sensors now provides a means of continuously monitoring the composition and thickness of the growing Hg1−xCdxTe film. 相似文献
7.
By means of in situ arsenic/phosphorus partial pressure control, the metastabilization of transitional surface structures during the coherent
reformation and flattening of InGaAs(P) dots has been achieved. Since coherently grown dots are maintained by strain accumulated
between the dots and a sublayer, the in situ replacement of arsenic/phosphorus in the several topmost monolayers changes the surface lattice parameter of the dots, and
a drastic change in surface structure (the flattening of the dots or their reformation) is induced. The transitional surfaces
being metastabilized were observed ex situ by a high-resolution scanning electron microscope and an atomic force microscope, and the process of dot reformation/flattening
was made clear. To show the application of in situ phosphidation (the replacement of arsenic by phosphorus) of dots, the step by step reformation of the dots was demonstrated
using an AsH3 pulse supply onto the flattened surface. The fabrication of graded-composition dots was attempted by the pulse supply of
TEGa or TMIn during the step by step reformation of dots, resulting in a large difference in the intensity of photoluminescence
(PL) between Ga-added and In-added dots. Furthermore, the temperature dependence of PL from the transitional structure between
dots and a flat surface has been investigated by means of capping the structure with GaAs overgrowth. The effects of dot phosphidation
on PL are discussed through comparison with unphosphidated dots. 相似文献
8.
Extrinsic p-type doping during molecular-beam epitaxy (MBE) growth represents an essential generic toolbox for advanced heterostructures
based on the HgCdTe material system: PiN diodes, mesa avalanche photodiodes (APD) or third-generation multispectral focal-plane
arrays. Today, arsenic appears to be the best candidate to fulfill this role and our group is actively working on its incorporation
during MBE growth, using an original radio frequency (RF) plasma source for arsenic. Such a cell is supposed to deliver a
monatomic As flux, and as expected we observed high As electrical activation rates after annealing short-wave (SW), mid-wave
(MW), and long-wave (LW) layers. At last, a couple of technological runs have been carried out in the MW range in order to
validate the approach on practical devices. p-on-n focal-plane arrays (FPA) have been fabricated using a mesa delineated technology on an As-on-In doped metallurgical heterojunction
layer grown on a lattice-matched CdZnTe layer (320 × 256, 30 μm pitch, 5 μm cutoff at 77 K). Observed diodes exhibit very interesting electro-optical characteristics: large shunt impedance, high quantum
efficiency, and no noticeable excess noise. The resulting focal-plane arrays were observed to be very uniform, leading to
high operabilities. Noise equivalent temperature difference (NETD) distributions are very similar to those observed with the
As ion-implanted p-on-n technology, fabricated in our laboratory as well. In our opinion, those excellent results demonstrate the feasibility of
our MBE in situ arsenic doping process. Good electrical activation rates and high-quality layers can be obtained. We believe that such an
approach allows precise control of the p-doping profile in the HgCdTe layer, which is necessary for advanced structure designs. 相似文献
9.
M.F. Vilela S.F. Harris R.E. Kvaas A.A. Buell M.D. Newton K.R. Olsson D.D. Lofgreen S.M. Johnson 《Journal of Electronic Materials》2009,38(8):1755-1763
In this paper, we show the versatility of using molecular-beam epitaxy (MBE) for the growth of the mercury cadmium telluride
(HgCdTe) system. Abrupt composition profiles, changes in doping levels or switching doping types are easily performed. It
is shown that high-quality material is achieved with Hg(1–x)Cd
x
Te grown by MBE from a cadmium mole fraction of x = 0.15 to x = 0.72. Doping elements incorporation as low as 1015 cm−3 for both n-type and p-type material as well as high incorporation levels >1018 cm−3 for both carrier types were achieved. X-ray curves, secondary-ion mass spectrometry (SIMS) data, Hall data, the influence
of doping incorporation with cadmium content and growth rate, etch pit density (EPD), composition uniformity determined from
Fourier-transform infrared (FTIR) transmission spectro- scopy, and surface defect maps from low to high x values are presented to illustrate the versatility and quality of HgCdTe material grown by MBE. All data presented in this
work are from layers grown on silicon (112) substrate. 相似文献
10.
Zhonghai Yu M. A. Mattson T. H. Myers K. A. Harris R. W. Yanka L. M. Mohnkern L. C. Lew Yan Voon L. R. Ram-Mohan R. G. Benz B. K. Wagner C. J. SummersBenz 《Journal of Electronic Materials》1995,24(5):685-690
Epitaxial growth of Hg-based semiconductors by molecular beam epitaxy (MBE) and metalorganic MBE (MOMBE) has progressed sufficiently
to shift emphasis to the control of factors limiting the yield of both materials and devices. This paper reports on anex-situ study to evaluate the suitability of reflectance and photoreflectance (PR) asin-situ characterization techniques for the growth of CdTe and HgCdTe. Photoreflectance yields information about CdTe layers, with
largest utility for doped and multi-layer structures. However, caution must be taken in interpretation of the spectra since
the near-bandedge PR spectra consists of multiple transitions and the E1 transition energy is very sensitive to the sample history. Photoreflectance appears to be of limited utility for HgCdTe single
layer growth with x<0.4. However, reflectance measurements of the E1 peak can be used to determine composition in HgCdTe single layers with an accuracy Δx = ±0.01, which can be useful for growth
control. A tight binding model was used to calculate the E1 peak energy as a function of bandgap for HgCdTe and HgTe/CdTe superlattices. Comparisons are made with experimental observations.
Surface interdiffusion in HgTe-CdTe superlattices was probed using reflectance measurements. 相似文献
11.
Y.H. ChangM.L. Huang P. ChangJ.Y. Shen B.R. ChenC.L. Hsu T.W. Pi M. Hong J. Kwo 《Microelectronic Engineering》2011,88(7):1101-1104
This work presents the in situ reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and synchrotron-radiation photoemission studies for the morphological and interfacial chemical characterization of in situ atomic layer deposited (ALD) Al2O3 on pristine molecular beam epitaxy (MBE) grown Ga-rich n-GaAs (1 0 0)-4 × 6 surface. Both the RHEED pattern and STM image demonstrated that the first cycle of ALD-Al2O3 process reacted immediately with the GaAs surface. As revealed by in situ synchrotron-radiation photoemission studies, two types of surface As atoms that have excess in charge in the clean surface served as reaction sites with TMA. Two oxidized states were then induced in the As 3d core-level spectra with chemical shifts of +660 meV and +1.03 eV, respectively. 相似文献
12.
Streit D.C. Umemoto D.K. Kobayashi K.W. Oki A.K. 《Electron Devices, IEEE Transactions on》1995,42(4):618-623
We have achieved successful monolithic integration of high electron mobility transistors and heterojunction bipolar transistors in the same microwave circuit. We have used selective molecular beam epitaxy and a novel merged processing technology to fabricate monolithic microwave integrated circuits that incorporate both 0.2 μm gate-length pseudomorphic InGaAs-GaAs HEMTs and 2 μm emitter-width GaAs-AlGaAs HBTs. The HEMT and HBT devices produced by selective MBE and fabricated using our merged HEMT-HBT process exhibited performance equivalent to devices fabricated using normal MBE and our baseline single-technology processes. The selective MBE process yielded 0.2 μm HEMT devices with gm=600 mS/mm and fT=70 GHz, while 2×10 μm2 HBT devices achieved β>50 and fT=21.4 GHz at Jc=2×104 A/cm2. The performance of both a 5-10 GHz HEMT LNA with active on-chip HBT regulation and a 20 GHz Darlington HBT amplifier are shown to be equivalent whether fabricated using normal or selective MBE 相似文献
13.
Many optoelectronic devices require contacts top-doped epitaxial layers. To achieve low contact resistance, the semiconductor has to be doped to high levels. Thep-dopants most commonly used are Be, Mg, and Zn. The contacts were formed by the sequential e-beam evaporation of 10 nm Pd,
≤5 nm Zn, 20 nm Pd and 40 nm Au layers onto a 0.2 μm thick Be-doped (5 × 1018 cm) GaAs layer grown by MBE. The minimum contact resistance of 0.04Ω-mm (≤1 × 10−7
Ω-cm2), as measured using the transmission line method, was obtained for contacts annealed at 500° C for 30s. These are the lowest
contact resistance values reported to date for alloyed contacts top-GaAs. 相似文献
14.
We have performed a preliminary investigation into the use of ZnSe bulk crystals fabricated by Sumitomo Electric Industries,
Ltd. as substrates for the epitaxial1 deposition of ZnSe-based materials and light emitting devices. A low temperature (<380
°C)in- situ cleaning process has been developed for the (100) oriented ZnSe wafers involving the use of a remotely generated atomic hydrogen
beam. The process produces a (1 × 1) atomically smooth ZnSe surface which is highly suitable for epitaxy. Hall-effect measurements
performed on nitrogen-doped ptype ZnSe/S.I. ZnSe epilayers have revealed free-hole concentrations in the homoepitaxial material
as high as 2.1 × 1017cm−3, so far, with room temperature and 77Khole mobility values of 20 and 100 cm2V
su−1
ins/su−1
, respectively. Finally, green light emitting diodes have been grown on the ZnSe wafers having Cd0.2Zn0.8Se/ ZnSe multiple quantum well active regions which have exhibited electroluminescence peak linewidths around 9.9 nm at room
temperature. 相似文献
15.
K. Eisenbeiser R. Droopad Z. Yu C. Overgaard J. Kulik J. Finder S. M. Smith S. Voight D. Penunuri 《Journal of Electronic Materials》2003,32(8):868-871
We have developed a process to grow epitaxial SrTiO3 (STO) on Si. This STO/Si substrate can then be used as a pseudo substrate for the further deposition of many other oxides
that are closely lattice matched to STO. The STO is grown by molecular-beam epitaxy (MBE) with a subsequent oxide layer deposited
either by MBE or sol-gel deposition. The pseudo substrate has been used to demonstrate ferroelectric devices and piezoelectric
devices. Ferroelectric capacitors using epitaxial BaTiO3 (BTO) show a memory window of 0.5 V; however, the retention time for these devices is short because of the depolarization
field caused by the silicon-oxide interface layer used to improve the band alignment of the BTO/Si interface. Surface acoustic
wave (SAW) resonators using epitaxial Pb(Zr,Ti)O3 show excellent response with a coupling coefficient of 4.6% and a velocity of 2,844 m/s. 相似文献
16.
Frontiers in the Growth of Complex Oxide Thin Films: Past,Present, and Future of Hybrid MBE
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Matthew Brahlek Arnab Sen Gupta Jason Lapano Joseph Roth Hai‐Tian Zhang Lei Zhang Ryan Haislmaier Roman Engel‐Herbert 《Advanced functional materials》2018,28(9)
Driven by an ever‐expanding interest in new material systems with new functionality, the growth of atomic‐scale electronic materials by molecular beam epitaxy (MBE) has evolved continuously since the 1950s. Here, a new MBE technique called hybrid‐MBE (hMBE) is reviewed that has been proven a powerful approach for tackling the challenge of growing high‐quality, multicomponent complex oxides, specifically the ABO3 perovskites. The goal of this work is to (1) discuss the development of hMBE in a historical context, (2) review the advantageous surface kinetics and chemistry that enable the self‐regulated growth of ABO3 perovskites, (3) layout the key components and technical challenges associated with hMBE, (4) review the status of the field and the materials that have been successfully grown by hMBE which demonstrate its general applicability, and (5) discuss the future of hMBE in regards to technical innovations and expansion into new material classes, which are aimed at expanding into industrial realm and at tackling new scientific endeavors. 相似文献
17.
J. E. Jensen J. A. Roth P. D. Brewer G. L. Olson J.J Dubray O. K. Wu R. D. Rajavel T. J. deLyon 《Journal of Electronic Materials》1998,27(6):494-499
Next-generation HgCdTe infrared detectors and detector arrays require the growth of multilayer heterojunction structures with
precisely controlled alloy composition and doping levels and minimal defect densities. Molecular beam epitaxy (MBE) provides
the ability to produce such structures. However, in the absence of a real-time, in situ control methodology the extreme sensitivity of HgCdTe layer quality and doping efficiency on fundamental MBE variable such
a substrate temperature and effusion cell flux provide serious challenges to the uniform and reproducible growth of such structures.
In this paper, we describe an integrated, multi-sensor approach for monitoring and controlling the variables that are most
important for MBE growth of HgCdTe device structures used in advanced multi-color infrared detectors and high speed, low-noise
avalanche photodiodes. Substrate temperature, effusion cell flux, and layer composition are monitored using absorption-edge
spectroscopy (ABES), optical flux monitoring (OFM), an spectroscopic ellipsometry (SE), respectively. Flexible, custom software
has been developed and implemented for analysis of sensor inputs and feedback control of the MBE system in response to those
inputs. The sensors and their application to growth of HgCdTe will be described, and the use of a custom software framework
for data analysis and system control will be discussed. 相似文献
18.
A diagram of the structural and morphological state of a Ge film on a Si(100) surface is constructed using in situ recording of the reflection high-energy electron diffraction patterns. The diagram involves the following regions: the continuous film, hut-and dome-shaped clusters, and dome-shaped clusters with misfit dislocations at the interface. The variation in the lattice parameters of the Ge film during MBE growth on the Si(100) surface is measured for the first time, and the oscillations of the variation in the lattice parameter for the (100) plane during two-dimensional layer-by-layer growth are found. 相似文献
19.
E. P. G. Smith G. M. Venzor Y. Petraitis M. V. Liguori A. R. Levy C. K. Rabkin J. M. Peterson M. Reddy S. M. Johnson J. W. Bangs 《Journal of Electronic Materials》2007,36(8):1045-1051
Small 15 μm unit-cell mid-wavelength infrared (MWIR) detectors have been fabricated and characterized at Raytheon Vision Systems (RVS)
to enable the development of high resolution, large format, infrared imaging systems. The detectors are fabricated using molecular
beam epitaxy (MBE) grown 4-in. HgCdTe-on-Si wafers with a p-on-n double layer heterojunction (DLHJ) device architecture. Advanced fabrication processes, such as inductively coupled plasma
(ICP) etching, developed for large format MBE-on-Si wafers and 20 μm unit-cell two-color triple layer heterojunction (TLHJ) focal plane arrays (FPAs) have been successfully extended and applied
to yield high performance 15 μm unit-cell single color detectors that compare favorably with state-of-the-art detectors with larger pitch. The measured
78 K MWIR cut-off wavelength for the fabricated detectors is near 5.5 μm, and the current–voltage characteristics of these devices exhibit strong reverse breakdown and RoA performance as a function
of temperature with diffusion limited performance extending to temperatures down to 120 K. 相似文献