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1.
W. Lei R. J. Gu J. Antoszewski J. Dell L. Faraone 《Journal of Electronic Materials》2014,43(8):2788-2794
In this work, GaSb is proposed as a new alternative substrate for the growth of HgCdTe via molecular beam epitaxy (MBE). Due to the smaller mismatch in both lattice constant and coefficient of thermal expansion between GaSb and HgCdTe, GaSb presents a better alternative substrate for the epitaxial growth of HgCdTe, in comparison to alternative substrates such as Si, Ge, and GaAs. In our recent efforts, a CdTe buffer layer technology has been developed on GaSb substrates via MBE. By optimizing the growth conditions (mainly growth temperature and VI/II flux ratio), CdTe buffer layers have been grown on GaSb substrates with material quality comparable to, and slightly better than, CdTe buffer layers grown on GaAs substrates, which is one of the state-of-the-art alternative substrates used in growing HgCdTe for the fabrication of mid-wave infrared detectors. The results presented in this paper indicate the great potential of GaSb to become the next generation alternative substrate for HgCdTe infrared detectors, demonstrating MBE-grown CdTe buffer layers with rocking curve (double crystal x-ray diffraction) full width at half maximum of ~60 arcsec and etch pit density of ~106 cm?2. 相似文献
2.
Study of HgCdSe Material Grown by Molecular Beam Epitaxy 总被引:1,自引:0,他引:1
Much progress has been made in developing high-quality HgCdTe/Si for large-area focal-plane array (FPA) applications. However,
even with all the material advances made to date, there is no guarantee that this technology will be mature enough to meet
the stringent FPA specifications required for long-wavelength infrared (LWIR) systems. With this in mind, the Army Research
Laboratory (ARL) has begun investigating HgCdSe material for infrared (IR) applications. Analogous to HgCdTe, HgCdSe is a
tunable semiconductor that can detect any wavelength of IR radiation through control of the alloy composition. In addition,
several mature, large-area bulk III–V substrates are nearly lattice matched to HgCdSe, giving this system a possible advantage
over HgCdTe, for which no scalable, bulk substrate technology exists. We have initiated a study of the growth of HgCdSe using
molecular beam epitaxy (MBE). Growth temperature and material flux ratios were varied to ascertain the best growth conditions.
Smooth surface morphology has been achieved using a growth temperature much lower than that used for HgCdTe. Additionally,
zero void defects were nucleated at these lower temperatures. Preliminary data suggest a linear relationship between the Se/Cd
flux ratio used during growth and the cutoff wavelength as measured by Fourier-transform infrared (FTIR) spectroscopy. 相似文献
3.
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
4.
Direct growth of CdZnTe/Si substrates for large-area HgCdTe infrared focal plane arrays 总被引:1,自引:0,他引:1
S. M. Johnson T. J. de Lyon C. A. Cockrum W. J. Hamilton T. Tung F. I. Gesswein B. A. Baumgratz L. M. Ruzicka O. K. Wu J. A. Roth 《Journal of Electronic Materials》1995,24(5):467-473
Direct epitaxial growth of high-quality 100lCdZnTe on 3 inch diameter vicinal {100}Si substrates has been achieved using molecular
beam epitaxy (MBE); a ZnTe initial layer was used to maintain the {100} Si substrate orientation. The properties of these
substrates and associated HgCdTe layers grown by liquid phase epitaxy (LPE) and subsequently processed long wavelength infrared
(LWIR) detectors were compared directly with our related efforts using CdZnTe/ GaAs/Si substrates grown by metalorganic chemical
vapor deposition (MOCVD). The MBE-grown CdZnTe layers are highly specular and have both excellent thickness and compositional
uniformity. The x-ray full-width at half-maximum (FWHM) of the MBE-grown CdZnTe/Si increases with composition, which is a
characteristic of CdZnTe grown by vapor phase epitaxy, and is essentially equivalent to our results obtained on CdZnTe/GaAs/Si.
As we have previously observed, the x-ray FWHM of LPE-grown HgCdTe decreases, particularly for CdZnTe compositions near the
lattice matching condition to HgCdTe; so far the best value we have achieved is 54 arc-s. Using these MBE-grown substrates,
we have fabricated the first high-performance LWIR HgCdTe detectors and 256 x 256 arrays using substrates consisting of CdZnTe
grown directly on Si without the use of an intermediate GaAs buffer layer. We find first that there is no significant difference
between arrays fabricated on either CdZnTe/Si or CdZnTe/GaAs/Si and second that the results on these Si-based substrates are
comparable with results on bulk CdZnTe substrates at 78K. Further improvements in detector performance on Si-based substrates
require a decrease in the dislocation density. 相似文献
5.
Uniform low defect density molecular beam epitaxial HgCdTe 总被引:3,自引:0,他引:3
J. Bajaj J. M. Arias M. Zandian D. D. Edwall J. G. Pasko L. O. Bubulac L. J. Kozlowski 《Journal of Electronic Materials》1996,25(8):1394-1401
This paper describes recent advances in MBE HgCdTe technology. A new 3 inch production molecular beam epitaxy (MBE) system,
Riber Model 32P, was installed at Rockwell in 1994. The growth technology developed over the years at Rockwell using the Riber
2300 R&D system was transferred to the 32P system in less than six months. This short period of technology transfer attests
to our understanding of the MBE HgCdTe growth dynamics and the key growth parameters. Device quality material is being grown
routinely in this new system. Further advances have been made to achieve better growth control. One of the biggest challenges
in the growth of MBE HgCdTe is the day-to-day control of the substrate surface temperature at nucleation and during growth.
This paper describes techniques that have led to growth temperature reproducibility within + - 1°C, and a variation in temperature
during substrate rotation within 0.5°C. The rotation of the substrate during growth has improved the uniformity of the grown
layers. The measured uniformity data on composition for a typical 3 cm × 3 cm MBE HgCdTe/CdZnTe shows the average and standard
deviation values of 0.229 and 0.0006, respectively. Similarly, the average and standard deviation for the layer thickness
are 7.5 and 0.06 μm, respectively. P-on-n LWIR test structure photodiodes fabricated using material grown by the new system
and using rotation during growth have resulted in high-performance (R0)A, quantum efficiency) devices at 77 and 40K. In addition, 128 × 28 focal plane arrays with excellent performance and operability
have been demonstrated. 相似文献
6.
M. Daraselia C. H. Grein S. Rujirawat B. Yang S. Sivananthan F. Aqariden H. D. Shih 《Journal of Electronic Materials》1999,28(6):743-748
Optical real-time in-situ sensors play a very important role in the processing of semiconductor devices because of their noncontact remote nature and
excellent compatibility with UHV systems. In this work, we report on progress in developing an in-situ temperature sensor for HgCdTe structures grown by molecular beam epitaxy (MBE). Based on the Fourier transform infrared (FTIR)
spectrometer, this sensor is capable of continuous real-time monitoring of the surface temperature, thickness and alloy composition
of HgCdTe epilayers. The accuracy and sensitivity of this FTIR technique were studied in all temperature ranges of interest.
Also compared are two different methods of temperature determination obtained from the normalized spectral radiance. The influence
of stray radiation and of sample holder rotation on the measurement accuracy have been studied. Reflectivity spectra for HgCdTe/CdZnTe(211)
and HgCdTe/CdTe(211)/Si(211) structures have been analyzed in real time in order to determine the layer thickness and alloy
composition for growing layers. Also discussed is a multilayer-structure optical model developed to solve the problem of composition
determination at early stages of growth. The application of this model for fitting the transmission spectra is demonstrated. 相似文献
7.
Double-axis x-ray rocking curve measurements have been used to nondestructively characterize the composition profile of HgCdTe
heterojunction photodiode structures grown by liquid phase epitaxy (LPE). In particular, the thickness and composition profile
of the thin graded-composition cap layer are determined through an empirical correlation between rocking curve parameters
and composition profiles measured by SIMS. Spatial maps of cap layer thickness and composition are generated from automated
measurements of x-ray rocking curves across a wafer. X-ray mapping has been instrumental in improving the spatial uniformity
of cap layers and in maintaining control of the growth process in Hg-rich LPE dipping reactors. 相似文献
8.
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
9.
10.
文章报道了采用液相外延方法,在碲锌镉衬底上进行碲锌镉薄膜缓冲层生长的情况,并且采用X光双晶衍射仪、X光形貌仪、红外傅里叶光谱仪、二次离子质谱仪等手段对碲锌镉薄膜进行了表征,碲锌镉薄膜具有较好地组分及均匀性,晶体结构质量也较好。采用碲锌镉缓冲结构生长了碲镉汞液相外延片,其碲锌镉与碲镉汞薄膜界面附近的杂质得到了有效的控制。 相似文献
11.
12.
Jae Jin Kim R. N. Jacobs L. A. Almeida M. Jaime-Vasquez C. Nozaki David J. Smith 《Journal of Electronic Materials》2013,42(11):3142-3147
A microstructural study of HgCdTe/CdTe/GaAs(211)B and CdTe/GaAs(211)B heterostructures grown using molecular beam epitaxy (MBE) was carried out using transmission electron microscopy and small-probe microanalysis. High-quality MBE-grown CdTe on GaAs(211)B substrates was demonstrated to be a viable composite substrate platform for HgCdTe growth. In addition, analysis of interfacial misfit dislocations and residual strain showed that the CdTe/GaAs interface was fully relaxed except in localized regions where GaAs surface polishing had caused small pits. In the case of HgCdTe/CdTe/GaAs(211)B, the use of thin HgTe buffer layers between HgCdTe and CdTe for improving the HgCdTe crystal quality was also investigated. 相似文献
13.
G. L. Olson J. A. Roth P. D. Brewer R. D. Rajavel D. M. Jamba J. E. Jensen B. Johs 《Journal of Electronic Materials》1999,28(6):749-755
We describe an integrated real-time sensing and control system for monitoring and controlling substrate temperature, layer
composition, and effusion cell flux during molecular beam epitaxial growth of HgCdTe epilayers for advanced IR detectors.
Substrate temperature is monitored in real-time using absorption-edge spectroscopy, allowing the temperature to be controlled
within 1.5°C of the desired setpoint. In situ spectroscopic ellipsometry (SE) is used for monitoring HgCdTe layer composition in real-time. A comprehensive temperature-
and composition-dependent dielectric function database has been recorded which allows the accurate and precise determination
of Hg1−xCdxTe layer composition over a wide range of x-values, from 0.2 to 0.42. The composition changes inferred from real-time SE measurements
obtained during growth of a two-layer structure are in excellent agreement with composition profiles obtained using post-growth
secondary ion mass spectroscopy analysis. The accuracy and precision of SE measurements conducted over multiple growth runs
are shown to be suitable for robust SE-based composition control. Changes in the Cd flux produced by a CdTe effusion cell
are detected using an atomic optical absorption method. This method allows changes in HgCdTe layer composition to be correlated
directly with variations in Cd flux. All of the in situ sensors are linked using a custom software framework to provide the foundation for real-time monitoring and control of HgCdTe
MBE growth of high performance infrared detector structures over a wide range of compositions, layer thicknesses, and substrate
temperatures. 相似文献
14.
Hg1-xCdxTe is an important material for infrared (IR) detection applications where the bandgap of the alloy varies from semimetal
to 1.4 eV. The large variation in bandgap energy with HgCdTe composition causes difficulty in controlling detector-cutoff
wavelength, particularly for the long-wavelength IR and very-long-wavelength infrared (VLWIR, greater than 12 μm) spectral
bands. Our ability to control the HgCdTe composition and compositional profile during growth by molecular beam epitaxy (MBE)
is improved significantly by using automated feedback control from spectroscopic ellipsometry (SE) measurements, where the
standard deviation in the error in composition has improved by a factor of 5, from σ=0.0081 to σ=0.0016. To improve our ability
to predict cutoff wavelength from IR transmission measurements, we have used a model of the absorption in HgCdTe to revise
our past empirical cutoff relationship to include the effect of compositional grading. We have achieved a mean detector-cutoff
wavelength of 14.1 μm and standard deviation of σ=0.25 μm for a series of 19 processed layers with a target cutoff of 14 μm.
The excellent control in VLWIR detector cutoff we have observed is attributed to automated compositional control and an improved
cutoff-prediction model. 相似文献
15.
M. Reddy J. M. Peterson S. M. Johnson T. Vang J. A. Franklin E. A. Patten W. A. Radford J. W. Bangs D. D. Lofgreen 《Journal of Electronic Materials》2009,38(8):1764-1770
This paper presents the progress in the molecular beam epitaxy (MBE) growth of HgCdTe on large-area Si and CdZnTe substrates
at Raytheon Vision Systems. We report a very high-quality HgCdTe growth, for the first time, on an 8 cm × 8 cm CdZnTe substrate.
This paper also describes the excellent HgCdTe growth repeatability on multiple 7 cm × 7 cm CdZnTe substrates. In order to
study the percentage wafer area yield and its consistency from run to run, small lots of dual-band long-wave infrared/long-wave
infrared triple-layer heterojunction (TLHJ) layers on 5 cm × 5 cm CdZnTe substrates and single-color double-layer heterojunction
(DLHJ) layers on 6-inch Si substrates were grown and tested for cutoff wavelength uniformity and micro- and macrovoid defect
density and uniformity. The results show that the entire lot of 12 DLHJ-HgCdTe layers on 6-inch Si wafers meet the testing
criterion of cutoff wavelength within the range 4.76 ± 0.1 μm at 130 K and micro- and macrovoid defect density of ≤50 cm−2 and 5 cm−2, respectively. Likewise, five out of six dual-band TLHJ-HgCdTe layers on 5 cm × 5 cm CdZnTe substrates meet the testing criterion
of cutoff wavelength within the range 6.3 ± 0.1 μm at 300 K and micro- and macrovoid defect density of ≤2000 cm−2 and 500 cm−2, respectively, on the entire wafer area. Overall we have found that scaling our HgCdTe MBE process to a 10-inch MBE system
has provided significant benefits in terms of both wafer uniformity and quality. 相似文献
16.
T. J. De Lyon J. E. Jensen I. Kasai G. M. Venzor K. Kosai J. B. de Bruin W. L. Ahlgren 《Journal of Electronic Materials》2002,31(3):220-226
Results are reported on the molecular-beam epitaxial (MBE) growth and electrical performance of HgCdTe midwave-infrared (MWIR)
detector structures. These devices are designed for operation in the 140–160 K temperature range with cutoff wavelengths ranging
from 3.4–3.8 μm at 140 K. Epitaxial structures, grown at 185°C on (211)B-oriented CdZnTe substrates, consisting of either
conventional two-layer P-n configurations or three-layer P-n-N configurations, were designed to examine the impact of device
performance on variation of the n-type base layer (absorber) thickness and the inclusion or omission of an underlying wide-bandgap
buffer layer. Devices were grown with absorber thicknesses of 3 μm, 5 μm, and 7 μm to examine the tradeoff between the spectral
response characteristic and the reverse-bias electrical performance. In addition, 5-μm-thick, wide-bandgap HgCdTe buffer layers,
whose CdTe mole fraction was approximately 0.1 larger than the absorber layer, were introduced into several device structures
to study the effect of isolating the device absorbing layer from the substrate/growth initiation interface. The MBE-grown
epitaxial wafers were processed into passivated, mesa-type, discrete device structures and diode mini arrays, which were tested
for temperature-dependent R0A product, quantum efficiency, spectral response, and the I-V characteristic at temperatures close to 140 K. External quantum
efficiencies of 75–79% were obtained with lateral optical-collection lengths of 7 μm. Analysis of the temperature dependence
of the diode R0A product indicates that the device impedance is limited by the diffusion current at temperatures above 140 K with typical
R0A values of 2×106 Ω cm2 for a detector cutoff of 3.8 μm at 140 K. An alloy composition anomaly at the absorbing-layer/buffer-layer interface is believed
to limit the observed R0A products to values approximately one order of magnitude below the theoretical limit projected for radiatively limited carrier
lifetime. Device electrical performance was observed to be improved through incorporation of a wide-bandgap buffer layer and
through reduction of the absorbing layer thickness. An optimum spectral response characteristic was observed for device structures
with 5-μm-thick absorbing layers. 相似文献
17.
M.F. Vilela G.K. Pribil K.R. Olsson D.D. Lofgreen 《Journal of Electronic Materials》2012,41(10):2937-2942
In this work, spectroscopic ellipsometry (SE) is demonstrated as a technique to calibrate growth temperature measurement devices (thermocouples and pyrometers) prior to real mercury cadmium telluride (HgCdTe) growth. A pyrometer is used to control the substrate temperature in molecular beam epitaxy (MBE) for the growth of HgCdTe-based material. It is known that a very narrow optimal growth temperature range exists for HgCdTe, typically ±5°C. A nonoptimal growth temperature will negatively impact on material quality by inducing growth defects, reducing composition uniformity, causing difficulty in controlling doping incorporation, promoting poor electronic properties, and having other adverse effects. Herein, we present a method for measuring and calibrating substrate temperature measurement equipment by using spectroscopic ellipsometry (SE) prior to real HgCdTe growth. This method is easy to implement, nondestructive, and reliable. The proposed method requires one substrate with a surface material with optical properties well known in the temperature range of interest, but not necessarily the same base material as the material to be grown. In the specific case of this work, we use epitaxial CdTe material on top of a Si substrate. This wafer was used to create a database of its optical properties as a function of temperature by using SE. From the collected optical parameters, a model is built and a fit is generated from the SE data collected. The temperature can then be determined by fitting the temperature-dependent SE measurements from this specific CdTe material. The angle offset and surface roughness parameters are also included in the model to account for changes in the average run-to-run angle variations and surface conditions over time. This work does not attempt to obtain an absolute temperature, but rather a reliable and repeatable relative temperature measurement. 相似文献
18.
19.
S. M. Johnson A. A. Buell M. F. Vilela J. M. Peterson J. B. Varesi M. D. Newton G. M. Venzor R. E. Bornfreund W. A. Radford E. P. G. Smith J. P. Rosbeck T. J. De Lyon J. E. Jensen V. Nathan 《Journal of Electronic Materials》2004,33(6):526-530
The heteroepitaxial growth of HgCdTe on large-area Si substrates is an enabling technology leading to the production of low-cost,
large-format infrared focal plane arrays (FPAs). This approach will allow HgCdTe FPA technology to be scaled beyond the limitations
of bulk CdZnTe substrates. We have already achieved excellent mid-wavelength infrared (MWIR) and short wavelength infrared
(SWIR) detector and FPA results using HgCdTe grown on 4-in. Si substrates using molecular beam epitaxy (MBE), and this work
was focused on extending these results into the long wavelength infrared (LWIR) spectral regime. A series of nine p-on-n LWIR
HgCdTe double-layer heterojunction (DLHJ) detector structures were grown on 4-in. Si substrates. The HgCdTe composition uniformity
was very good over the entire 4-in. wafer with a typical maximum nonuniformity of 2.2% at the very edge of the wafer; run-to-run
composition reproducibility, realized with real-time feedback control using spectroscopic ellipsometry, was also very good.
Both secondary ion mass spectrometry (SIMS) and Hall-effect measurements showed well-behaved doping and majority carrier properties,
respectively. Preliminary detector results were promising for this initial work and good broad-band spectral response was
demonstrated; 61% quantum efficiency was measured, which is very good compared to a maximum allowed value of 70% for a non-antireflection-coated
Si surface. The R0A products for HgCdTe/Si detectors in the 9.6-μm and 12-μm cutoff range were at least one order of magnitude below typical
results for detectors fabricated on bulk CdZnTe substrates. This lower performance was attributed to an elevated dislocation
density, which is in the mid-106 cm−2 range. The dislocation density in HgCdTe/Si needs to be reduced to <106 cm−2 to make high-performance LWIR detectors, and multiple approaches are being tried across the infrared community to achieve
this result because the technological payoff is significant. 相似文献
20.
L. O. Bubulac J. Bajaj W. E. Tennant M. Zandian J. Pasko W. V. Mc Levige 《Journal of Electronic Materials》1996,25(8):1312-1317
This work presents characterization of implanted and annealed double layer planar heterostructure HgCdTe for p-on-n photovoltaic
devices. Our observation is that compositional redistribution in the structure during implantation/ annealing process differs
from that expected from classical composition gradient driven interdiffusion and impacts the placement of the electrical junction
with respect to the metallurgical heterointerface, which in turn affects quantum efficiency and RoA. The observed anomalous interdiffusion results in much wider cap layers with reduced composition difference between base
and cap layer composition. The compositional redistribution can, however, be controlled by varying the material structure
parameters and the implant/anneal conditions. Examples are presented for dose and implanted species variation. A model is
proposed based on the fast diffusion in the irradiation induced damage region of the ion implantation. In addition, we demonstrate
spatial uniformity obtained on molecular beam epitaxy (MBE) material of the compositional and implanted species profile. This
reflects spatial uniformity of the ion implantation/annealing Processes and of the MBE material characteristics. 相似文献