共查询到14条相似文献,搜索用时 15 毫秒
1.
R. Haakenaasen H. Steen E. Selvig T. Lorentzen A. D. Van Rheenen L. Trosdahl-Iversen H. Syversen D. Hall N. Gordon 《Journal of Electronic Materials》2005,34(6):922-927
Imaging one-dimensional (1-D) and two-dimensional (2-D) arrays of mid-wavelength infrared (MWIR) and long-wavelength infrared
(LWIR) planar photodiodes were fabricated by ion milling of vacancy-doped molecular beam epitaxy CdxHg1−xTe layers. Sixty-four-element 1-D arrays of 26×26 μm2 or 26×56 μm2 diodes were processed. Zero-bias resistance-area values (R0A) at 77 K of 4×106 Θcm2 at cutoff wavelength λCO=4.5 μm were measured, as well as high quantum efficiencies. To avoid creating a leakage current during ball bonding to the
1-D array diodes, a ZnS layer was deposited on top of the CdTe passivation layer, as well as extra electroplated Au on the
bonding pads. The best measured noise equivalent temperature difference (NETD) on a LWIR array was 8 mK, with a median of
14 mK for the 42 operable diodes. The best measured NETD on a MWIR array was 18 mK. Two-D arrays showed reasonably good uniformity
of R0A and zero-bias current (I0) values. The first 64×64 element 2-D array of 16×16 μm2 MWIR diodes has been hybridized to read-out electronics and gave median NETD of 60 mK. 相似文献
2.
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
3.
R. Haakenaasen T. Colin H. Steen L. Trosdahl-Iversen 《Journal of Electronic Materials》2000,29(6):849-852
Ion milling has been used to type convert molecular beam epitaxy vacancy-doped CdxHg1−xTe, and electron beam induced current measurements have been performed to study the pn-junction depth dependence on milling
time, milling current and vacancy concentration. The junction depth seems to initially increase linearly with time for depths
up to ∼ 4 μm, then possibly as the square root of time at larger depth. For given x, the depth increases with decreasing vacancy
concentration. For the same annealing temperature, high x samples have lower carrier concentration and greater junction depth
than low x samples. Up to 4 μm, junction depth is proportional to milling current density as well as milling time. 相似文献
4.
J. N. Johnson L. A. Almeida J. D. Benson J. H. Dinan M. Martinka 《Journal of Electronic Materials》1998,27(6):657-660
CdZnTe wafers were inserted into a multi-chamber processing facility without prior preparation, cleaned by exposure to an
electron cyclotron resonance Ar/H2 plasma, and used as substrates for molecular beam epitaxy of HgCdTe. Changes induced in the wafer near-surface region during
the cleaning step were monitored using in situ spectroscopic ellipsometry. Ellipsometric data were subsequently modeled to provide the time evolution of the thickness of
a native overlayer. Auger electron spectra were consistent with surfaces free of residual contamination and which had the
stoichiometry of the underlying bulk. Surface roughness values of 0.4 nm were obtained ex situ using interferometric microscopy. Electron diffraction patterns of plasma prepared wafers heated to 185°C (the temperature
required for HgCdTe molecular beam epitaxy) were streaked. Structural and electrical characteristics of epilayers grown on
these substrates were found to be comparable to those deposited on wafers prepared using a conventional wet chemical process.
This demonstrates an important step in an all-vacuum approach to HgCdTe detector fabrication. 相似文献
5.
Molecular beam epitaxy growth of high-quality HgCdTe LWIR layers on polished and repolished CdZnTe substrates 总被引:2,自引:0,他引:2
R. Singh S. Velicu J. Crocco Y. Chang J. Zhao L. A. Almeida J. Markunas A. Kaleczyc J. H. Dinan 《Journal of Electronic Materials》2005,34(6):885-890
We report here molecular beam epitaxy (MBE) mercury cadmium telluride (HgCdTe) layers grown on polished and repolished substrates
that showed state-of-the-art optical, structural, and electrical characteristics. Many polishing machines currently available
do not take into account the soft semiconductor materials, CdZnTe (CZT) being one. Therefore, a polishing jig was custom designed
and engineered to take in account certain physical parameters (pressure, substrate rotational frequency, drip rate of solution
onto the polishing pad, and polishing pad rotational velocity). The control over these parameters increased the quality, uniformity,
and the reproducibility of each polish. EPIR also investigated several bromine containing solutions used for polishing CZT.
The concentration of bromine, as well as the mechanical parameters, was varied in order to determine the optimal conditions
for polishing CZT. 相似文献
6.
J. N. Johnson L. A. Almeida M. Martinka J. D. Benson J. H. Dinan 《Journal of Electronic Materials》1999,28(6):817-820
Without any additional preparation, Cd1−yZnyTe (211)B (y∼3.5%) wafers were cleaned by exposure to an electron cyclotron resonance (ECR) Ar/H2 plasma and used as substrates for HgCdTe molecular beam epitaxy. Auger electron spectra were taken from as-received wafers,
conventionally prepared wafers (bromine: methanol etching, followed by heating to 330–340°C), and wafers prepared under a
variety of ECR process conditions. Surfaces of as-received wafers contained ∼1.5 monolayers of contaminants (oxygen, carbon,
and chlorine). Conventionally prepared wafers had ∼1/4 monolayer of carbon contamination, as well as excess tellurium and/or
excess zinc depending on the heating process used. Auger spectra from plasma-treated CdZnTe wafers showed surfaces free from
contamination, with the expected stoichiometry. Stoichiometry and surface cleanliness were insensitive to the duration of
plasma exposure (2–20 s) and to changes in radio frequency input power (20–100 W). Reflection high energy electron diffraction
patterns were streaked indicating microscopically smooth and ordered surfaces. The smoothness of plasma-etched CdZnTe wafers
was further confirmed ex situ using interferometric microscopy. Surface roughness values of ∼0.4 nm were measured. Characteristics of HgCdTe epilayers
deposited on wafers prepared with plasma and conventional etching were found to be comparable. For these epilayers, etch pit
densities on the order of 105 cm−2 have been achieved. ECR Ar/H2 plasma cleaning is now utilized at Night Vision and Electronic Sensors Directorate as the baseline CdZnTe surface preparation
technique. 相似文献
7.
R. Ashokan N. K. Dhar B. Yang A. Akhiyat T. S. Lee S. Rujirawat S. Yousuf S. Sivananthan 《Journal of Electronic Materials》2000,29(6):636-640
Molecular beam epitaxy technique has been used to grow double layer heterostructure mercury cadmium telluride materials on
silicon substrates for infrared detection in the mid-wavelength infrared transmission band. Test structures containing square
diodes with variable areas from 5.76 × 10−6 cm2 to 2.5×10−3 cm2 are fabricated on them. The p on n planar architecture is achieved by selective arsenic ion implantation. The absorber layer
characteristics for the samples studied here include a full width at half maximum of 100–120 arcsec from x-ray rocking curve,
the electron concentration of 1−2 × 1015 cm−3 and mobility 3−5 × 104 cm2/V-s, respectively at 80 K from Hall measurements. The minority carrier lifetime measured by photoconductive decay measurements
at 80 K varied from 1 to 1.2 μsec. A modified general model for the variable area I–V analysis is presented. The dark current-voltage
measurements were carried out at 80 K and an analysis of the dependence of zero-bias impedance on the perimeter/area ratio
based on bulk, surface generation-recombination, and lateral currents are presented. The results indicate state-of-the art
performance of the diodes in the midwavelength infrared region. 相似文献
8.
Heteroepitaxy of HgCdTe (211)B on Ge substrates by molecular beam epitaxy for infrared detectors 总被引:3,自引:0,他引:3
J. P. Zanatta P. Ferret G. Theret A. Million M. Wolny J. P. Chamonal G. Destefanis 《Journal of Electronic Materials》1998,27(6):542-545
Epitaxial growth of (211)B CdTe/HgCdTe has been achieved on two inch germanium (Ge) by molecular beam epitaxy (MBE). Germanium
was chosen as an alternative substrate to circumvent the weaknesses of CdZnTe wafers. The ease of surface preparation makes
Ge an attractive candidate among many other alternative substrates. Best MBE CdTe growth results were obtained on (211) Ge
surfaces which were exposed to arsenic and zinc fluxes prior to the MBE growth. This surface preparation enabled CdTe growth
with B-face crystallographic polarity necessary for the HgCdTe growth. This process was reproducible, and produced a smooth
and mirror-like surface morphology. The best value of the {422} x-ray double diffraction full width at half maximum measured
from the HgCdTe layer was 68 arc-s. We present the 486 point maps of FWHM statistical values obtained from CdTe/Ge and HgCdTe/CdTe/Ge.
High resolution microscopy electron transmission and secondary ion mass spectroscopy characterization results are also presented
in this paper. High-performance middle wavelength infrared HgCdTe 32-element photodiode linear arrays, using the standard
LETI/LIR planar n-on-p ion implanted technology, were fabricated on CdTe/Ge substrates. At 78K, photodiodes exhibited very
high R0A figure of merit higher than 106 Ωcm−2 for a cutoff wavelength of 4.8 μm. Excess low frequency noise was not observed below 150K. 相似文献
9.
Molecular beam epitaxy HgCdTe growth-induced void defects and their effect on infrared photodiodes 总被引:3,自引:0,他引:3
J. M. Arias M. Zandian J. Bajaj J. G. Pasko L. O. Bubulac S. H. Shin R. E. De Wames 《Journal of Electronic Materials》1995,24(5):521-524
We have carried out a study and identified that MBE HgCdTe growth-induced void defects are detrimental to long wavelength
infrared photodiode performance. These defects were induced during nucleation by having surface growth conditions deficient
in Hg. Precise control and reproducibility of the CdZnTe surface temperature and beam fluxes are required to minimize such
defects. Device quality material with void defect concentration values in the low 102 cm2 range were demonstrated. 相似文献
10.
M. F. Vilela A. A. Buell M. D. Newton G. M. Venzor A. C. Childs J. M. Peterson J. J. Franklin R. E. Bornfreund W. A. Radford S. M. Johnson 《Journal of Electronic Materials》2005,34(6):898-904
Middle wave infrared (MWIR) HgCdTe p-on-n double-layer heterojunctions (DLHJs) for infrared detector applications have been
grown on 100-mm Si (112) substrates by molecular beam epitaxy (MBE) for large format 2,560×512 focal plane arrays (FPAs).
In order to meet the performance requirements needed for these FPAs, cutoff and doping uniformity across the 100-mm wafer
are crucial. Reflection high-energy electron diffraction (RHEED), secondary ion mass spectrometry (SIMS), Fourier transform
infrared spectrometry (FTIR), x-ray, and etch pit density (EPD) were monitored to assess the reproducibility, uniformity,
and quality of detector material grown. Material properties demonstrated include x-ray full width half maximum (FWHM) as low
as 64 arc-sec, typical etch pit densities in mid-106 cm−2, cutoff uniformity below 5% across the full wafer, and typical density of macrodefects <1000 cm−2. The detector quality was established by using test structure arrays (TSAs), which include miniarray diodes with the similar
pitch as the detector array for easy measurement of critical parameters such as diode I-V characteristics and detector quantum
efficiency. Typical I-V curves show excellent R0A products and strong reverse breakdown characteristics. Detector quantum efficiency was measured to be in the 60–70% range
without an antireflection coating. 相似文献
11.
T. C. Fu N. Newman E. Jones J. S. Chan X. Liu M. D. Rubin N. W. Cheung E. R. Weber 《Journal of Electronic Materials》1995,24(4):249-255
Since the growth of GaN using molecular beam epitaxy (MBE) occurs under metastable growth conditions, activated nitrogen is
required to drive the forward synthesis reaction. In the process of exciting the nitrogen using a plasma or ion-beam source,
species with large kinetic energies are generated. Impingement on the growth surface by these species can result in subsurface
damage to the growing film, as well as an enhancement of the reverse decomposition reaction rate. In this study, we investigate
the effect of the kinetic energy of the impinging nitrogen ions during growth on the resulting optical and structural properties
of GaN films. Strong band-edge photoluminescence and cathodoluminescence are found when a kinetic energy of ∼10 eV are used,
while luminescence is not detectable when the kinetic energies exceeds 18 eV. Also, we find that the use of conductive SiC
substrates results in more homogeneous luminescence than the use of insulating sapphire substrates. This is attributed to
sample surface charging in the case of sapphire substrates and subsequent variation in the incident ion flux and kinetic energy
across the growth surface. This study clearly shows that the quality of GaN films grown by MBE are presently limited by damage
from the impingement of high energy species on the growth surface. 相似文献
12.
M. Daraselia G. Brill J. W. Garland V. Nathan S. Sivananthan 《Journal of Electronic Materials》2000,29(6):742-747
In this work in-situ spectroscopic ellipsometry (SE) has been applied for the simultaneous determination of the growth temperature
and alloy composition for the epitaxial Cd1−xZnxTe(211)/Si(211) structure. The optical dielectric functions of CdTe and Cd0.96Zn0.04Te (CZT) epilayers were studied as a function of temperature both ex-situ and in-situ in the range from 1.6 eV to 4.5 eV.
We employed parametric models for the simulation of the optical properties of CZT at and between the critical points (CP)
E0, E0 + Δ0, E1, E1 + Δ1, E2(Σ) and E2(Σ). Critical point energies and line widths for Cd1−xZnxTe were obtained through the fitting process, which included both zero order and higher order derivatives of the SE pseudo
dielectric function. The dependence of the different critical points on Zn concentration x is discussed. It has been demonstrated
that the energy of the weak E0 + Δ0 transition can be used to measure composition, while the E1 energy can be used as a real-time temperature measure. The model parameters were optimized through the simultaneous analysis
of multiple data sets, and the temperature dependent model was developed for in-situ application. Our analysis is estimated
to produce uncertainties of only ±0.5°C in measuring the temperature and ±0.5% in measuring the composition of only the zero
order dielectric function is being fitted. The effects of a surface overlayer, of reflected beam deflections, and of other
experimental problems on the overall accuracy, are discussed as well as ways to improve the in-situ SE data quality. 相似文献
13.
Eva M. Campo Thomas Hierl James C. M. Hwang Yuanping Chen Gregory Brill 《Journal of Electronic Materials》2005,34(6):953-956
For the first time, focused ion beam milling, secondary electron microscopy, and transmission electron microscopy were used
to examine in depth morphological defects during epitaxial growth of CdTe and CdSeTe on Si. Contrary to the literature regarding
the formation of morphological defects at the epi/substrate interface, the present defects appear to originate from either
the CdTe/CdSeTe interface or 3–4 μm above the CdTe/Si interface where the growth was interrupted and the substrate temperature
was temporarily raised. This suggests a correlation between defect nucleation and either shutter movement or growth interruption. 相似文献
14.
We study the adsorption of Hg on CdTe(211)B using an 88-wavelength spectroscopic ellipsometer mounted on a commercial, molecular
beam epitaxy (MBE) chamber. A detailed analysis of the pseudo-dielectric function shows that Hg is present at the surface
both in chemisorbed and physisorbed form. Effective medium models for a mixture of chemisorbed and physisorbed Hg on the microscopically
rough CdTe surface could not fit our data. However, a proposed model in which a partial layer of physisorbed Hg sits on top
of a partial layer of chemisorbed Hg fits the measured pseudo-dielectric function well and yields precise values for the thicknesses
of the chemisorbed and the physisorbed Hg layers. These values change in the expected manner as a function of Hg flux, temperature,
and Te coverage. An analysis of the uncertainty in the measured thicknesses is carried out in detail, and a study of the limitations
of the ellipsometer used for this study is presented. The effects of these limitations on the precision and accuracy of in-situ
data are enumerated. 相似文献