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[show abstract]
[hide abstract]
ABSTRACT: An initial investigation of the use of atomic nitrogen for controlled p-type doping of wide-bandgap Hg0.3Cd0.7Te (x=0.7) is reported. Mixtures of argon and nitrogen, ranging in nitrogen concentration from 0.1% to 100%, have been utilized
to demonstrate well-controlled nitrogen incorporation in the 1016cm−3 to 1020cm−3 range using total gas flow rates of 0.3sccm to 4.0sccm and radiofrequency (RF) powers of 100W to 400W. Nitrogen doping
exhibits several desirable attributes including abrupt turn-on and turn-off and minimal sensitivity to variations in growth
temperature and HgCdTe composition, with no negative effects on HgCdTe dislocation density and morphology. Preliminary electrical
measurements indicate primarily n-type behavior in the 1014cm−3 to 1015cm−3 range in as-grown x=0.7 HgCdTe and CdTe films doped with nitrogen at 1018cm−3 to 1020cm−3 concentrations, while ZnTe films have exhibited p-type electrical activity with hole concentrations approaching 1020cm−3.
Journal of Electronic Materials 08/2008; 37(9):1420-1425. · 1.47 Impact Factor
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E. P. G. Smith,
E. A. Patten,
P. M. Goetz,
G. M. Venzor,
J. A. Roth,
B. Z. Nosho,
J. D. Benson,
A. J. Stoltz,
J. B. Varesi, J. E. Jensen,
S. M. Johnson,
W. A. Radford
[show abstract]
[hide abstract]
ABSTRACT: High-performance 20-µm unit-cell two-color detectors using an n-p+-n HgCdTe triple-layer heterojunction (TLHJ) device architecture grown by molecular beam epitaxy (MBE) on (211)-oriented CdZnTe
substrates with midwavelength (MW) infrared and long wavelength (LW) infrared spectral bands have been demonstrated. Detectors
with nominal MW and LW cut-off wavelengths of 5.5 µm and 10.5 µm, respectively, exhibit 78 K LW performance with >70 % quantum
efficiency, reverse bias dark currents below 300 pA, and RA products (zero field of view, 150-mV bias) in excess of 1×103 Ωcm2. Temperature-dependent current-voltage (I–V) detector measurements show diffusion-limited LW dark current performance extending
to temperatures below 70 K with good operating bias stability (150 mV ± 50 mV). These results reflect the successful implementation
of MBE-grown TLHJ detector designs and the introduction of advanced photolithography techniques with inductively coupled plasma
(ICP) etching to achieve high aspect ratio mesa delineation of individual detector elements with benefits to detector performance.
These detector improvements complement the development of high operability large format 640×480 and 1280×720 two-color HgCdTe
infrared focal plane arrays (FPAs) to support third generation forward looking infrared (FLIR) systems.
Journal of Electronic Materials 05/2006; 35(6):1145-1152. · 1.47 Impact Factor
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E. P. G. Smith,
L. T. Pham,
G. M. Venzor,
E. M. Norton,
M. D. Newton,
P. M. Goetz,
V. K. Randall,
A. M. Gallagher,
G. K. Pierce,
E. A. Patten, [......],
W. A. Radford,
L. M. Giegerich,
J. M. Edwards,
S. M. Johnson,
S. T. Baur,
J. A. Roth,
B. Nosho,
T. J. De Lyon, J. E. Jensen,
R. E. Longshore
[show abstract]
[hide abstract]
ABSTRACT: Raytheon Vision Systems (RVS, Goleta, CA) in collaboration with HRL Laboratories (Malibu, CA) is contributing to the maturation
and manufacturing readiness of third-generation, dual-color, HgCdTe infrared staring focal plane arrays (FPAs). This paper
will highlight data from the routine growth and fabrication of 256×256 30-µm unit-cell staring FPAs that provide dual-color
detection in the mid-wavelength infrared (MWIR) and long wavelength infrared (LWIR) spectral regions. The FPAs configured
for MWIR/MWIR, MWIR/LWIR, and LWIR/LWIR detection are used for target identification, signature recognition, and clutter rejection
in a wide variety of space and ground-based applications. Optimized triple-layer heterojunction (TLHJ) device designs and
molecular beam epitaxy (MBE) growth using in-situ controls has contributed to individual bands in all dual-color FPA configurations
exhibiting high operability (>99%) and both performance and FPA functionality comparable to state-of-the-art, single-color
technology. The measured spectral cross talk from out-of-band radiation for either band is also typically less than 10%. An
FPA architecture based on a single-mesa, single-indium bump, and sequential-mode operation leverages current single-color
processes in production while also providing compatibility with existing second-generation technologies.
Journal of Electronic Materials 05/2004; 33(6):509-516. · 1.47 Impact Factor
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R. A. Coussa,
A. M. Gallagher,
K. Kosai,
L. T. Pham,
G. K. Pierce,
E. P. Smith,
G. M. Venzor,
T. J. De Lyon, J. E. Jensen,
B. Z. Nosho,
J. A. Roth,
J. R. Waterman
[show abstract]
[hide abstract]
ABSTRACT: For small pixel, infrared (IR) focal plane arrays (FPAs), Raytheon Vision Systems’ architecture for integrated, dual-band
detectors uses the sequential mode of the n-p+-n configuration. There is a single indium bump per pixel, leaving the p+ layer floating, and the operating polarity of the bias selects the spectral sensitivity by reverse-biasing the active p-n
junction. Photogenerated minority carriers in the absorber layer of the forward-biased inactive photodiode are lost through
recombination. This paper is the first report of a new optical crosstalk mechanism that occurs in sequential-mode, dual-band
detectors. In the long-wavelength mode under out-of-band, short-wavelength illumination, radiative recombination yields emission
near the bandgap energy of the short-wavelength absorber layer, resulting in a spurious short-wavelength response that appears
as spectral crosstalk. We present experimental and device modeling results on the spectral crosstalk in molecular-beam-epitaxy-grown
HgCdTe arrays with the cutoff wavelength of both bands in the 4–5-µm range.
Journal of Electronic Materials 05/2004; 33(6):517-525. · 1.47 Impact Factor
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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
[show abstract]
[hide abstract]
ABSTRACT: 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.
Journal of Electronic Materials 01/2004; 33(6):526-530. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: 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.
Journal of Electronic Materials 02/2002; 31(3):220-226. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The application of spectroscopic ellipsometry (SE) for real-time composition determination during molecular beam epitaxy (MBE)
growth of Hg1−xCdxTe alloys with x>0.5 is reported. Techniques previously developed for SE determination of composition in long-wavelength infrared
(LWIR) HgCdTe have been successfully extended to near-infrared HgCdTe avalanche photodiode (APD) device structures with x
values in the range of 0.6–0.8. Ellipsometric data collected over a spectral range of 1.7–5 eV were used to measure depth
profiles of HgCdTe alloy composition through the use of an optical model of the growth surface. The optical model used a dielectric-function
database collected through the growth of a set of HgCdTe calibration samples with x ranging from 0.6 to 0.8. The sensitivity
of this SE method of composition determination is estimated to be Δx ∼0.0002 at x=0.6, which is sufficiently low to sense
composition changes arising from flux variations of less than 0.1%. Errors in composition determination because of Hg-flux
variations appear to be inconsequential, while substrate-temperature fluctuations have been observed to alter the derived
composition at a rate of −0.0004/°C. By comparing the composition inferred from SE and postgrowth 300 K IR transmission measurements
on a set of APD device structures, the run-to-run precision of the Se-derived composition (at x=0.6) is estimated to be ±0.0012,
which is equivalent to the precision achieved with the same instrumentation during the growth of mid-wavelength infrared (MWIR)
HgCdTe alloys in the same MBE system.
Journal of Electronic Materials 01/2002; 31(7):688-693. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: This report presents the results of research on compliant substrate behavior in III-V semiconductors grown by molecular beam epitaxy (MBE) on thin (50-80A) InGaAs layers on GaAs, and in II-VI semiconductors (HgCdTe, CdTe, ZnTe) grown on thin Si(211) layers on Si(100). A comprehensive experimental study was conducted utilizing spectroscopic ellipsometry, transmission electron microscopy, and atomic force microscopy at various stages in the fabrication and processing of the compliant layers and during MBE growth on those layers. Contrary to earlier reports by other investigators, we obtained no evidence for defect reduction or solid phase atomic rearrangement due to substrate compliancy in either of the III-V or II-V systems studied here. We conclude that the early reports of compliancy may have been erroneous interpretation of limited experimental data. Indeed, a theoretical consideration of stress relief mechanics in semiconductor thin films suggests that many of the proposed compliancy mechanisms are not feasible. Although no evidence of substrate compliancy was obtained, we were nevertheless successful in growing high quality II-VI layers by MBE on thin Si(211) layers bonded to Si(100) substrates. This has important implications for monolithic integration of HgCdTe infrared focal plane arrays with readout circuitry fabricated in Si(100) substrates.
10/2001;
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[show abstract]
[hide abstract]
ABSTRACT: We have developed the capability to grow HgCdTe mid-wave infrared radiation double-layer heterojunctions (MWIR DLHJs) on 4″
Si wafers by molecular beam epitaxy (MBE), and fabricate devices from these wafers that are comparable to those produced by
mature technologies. Test data show that the detectors, which range in cutoff wavelength over 4–7 μm, are comparable to the
trendline performance of liquid phase epitaxy (LPE)-grown material. The spectral characteristics are similar, with a slight
decrease in quantum efficiency attributable to the Si substrate. With respect to R0A, the HgCdTe/Si devices are closer to the theoretical radiative-limit than LPE-grown detectors. Known defect densities in
the material have been correlated to device performance through a simple model. Slight 1/f noise increases were measured in
comparison to the LPE material, but the observed levels are not sufficient to significantly degrade focal plane array (FPA)
performance. In addition to discrete detectors, two FPA formats were fabricated. 128×128 FPAs show MWIR sensitivity comparable
to mature InSb technology, with pixel operability values in excess of 99%. A 640×480 FPA further demonstrates the high-sensitivity
and high-operability capabilities of this material.
Journal of Electronic Materials 05/2001; 30(6):566-573. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: HgCdTe p-on-n double layer heterojunctions (DLHJs) for mid-wave infrared (MWIR) detector applications have been grown on 100
mm (4 inch) diameter (211) silicon substrates by molecular beam epitaxy (MBE). The structural quality of these films is excellent,
as demonstrated by x-ray rocking curves with full widths at half maximum (FWHMs) of 80–100 arcsec, and etch pit densities
from 1 106 to 7 106 cm−2. Morphological defect densities for these layers are generally less than 1000 cm−2. Improving Hg flux coverage of the wafer during growth can reduce void defects near the edges of the wafers. Improved tellurium
source designs have resulted in better temporal flux stability and a reduction of the center to edge x-value variation from
9% to only 2%. Photovoltaic MWIR detectors have been fabricated from some of these 100mm wafers, and the devices show performance
at 140 K which is comparable to other MWIR detectors grown on bulk CdZnTe substrates by MBE and by liquid phase epitaxy.
Journal of Electronic Materials 05/2001; 30(6):619-622. · 1.47 Impact Factor
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S. M. Johnson,
J. L. Johnson,
W. J. Hamilton,
D. B Leonard,
T. A. Strand,
E. A. Patten,
J. M. Peterson,
J. H. Durham,
V. K. Randall,
T. J. deLyon, J. E. Jensen,
M. D. Gorwitz
[show abstract]
[hide abstract]
ABSTRACT: As the number of bands and the complexity of HgCdTe multicolor structures increases, it is desirable to minimize the lattice
mismatch at growth interfaces within the device structure in order to reduce or eliminate mismatch dislocations at these interfaces
and potential threading dislocations that can degrade device performance. To achieve this we are investigating the use of
Hg1−x−yCdxZnyTe quaternary alloys which have an independently tunable lattice constant and bandgap. Lattice matching in Hg1−x−yCdxZnyTe structures can be achieved using small additions of Zn (y<0.015) to HgCdTe ternary alloys. We have investigated some of
the basic properties of Hg1−x−yCdxZnyTe materials with x≈0.31 and 0≤y≤0.015. The quaternary layers were grown on (112)CdZnTe substrates using MBE and the amount
of Zn in the layers was determined from calibrated SIMS measurements. As expected, the lattice constant decreased and the
bandgap increased as Zn was added to HgCdTe to form Hg1−x−yCdxZnyTe. Hall-effect results for both n-type (In) and p-type (As) Hg1−x−yCdxZnyTe layers were very similar to HgCdTe control samples. We have also utilized x-ray rocking curve measurements with (246) asymmetric
reflections as a novel sensitive technique to determine the correct amount of Zn needed to achieve lattice matching at an
interface. MWIR/LWIR n-p-n two-color triple-layer heterojunction structures were grown to evaluate the effects of minimizing
the lattice mismatch between the widest bandgap p-type collector layer, using Hg1−x−yCdxZnyTe, and the HgCdTe MWIR and LWIR collector layers and compared to structures that did not incorporate the quaternary. Sequential
mode two-color detectors were fabricated using a 256 × 256, 30 µm unit cell design. There were several interesting findings.
Macro defects predominantly affected the LWIR band (Band 2) operability and had little effect on the MWIR band (Band 1). The
incorporation of Hg1−x−yCdxZnyTe p-type collector layers had little effect on MWIR detector performance, but overall the LWIR performance was generally
better. These initial detector results indicate that the use of Hg1−x−yCdxZnyTe alloys in multicolor detector structures are potentially promising and should be pursued further.
Journal of Electronic Materials 05/2000; 29(6):680-686. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: 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.
Journal of Electronic Materials 05/1999; 28(6):749-755. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We review the rapid progress that has been made during the past three years in the heteroepitaxial growth of HgCdTe infrared
detector device structures on Si substrates by molecular-beam epitaxy. The evolution of this technology has enabled the fabrication
of high performance, large-area HgCdTe infrared focal-plane arrays on Si substrates. A key element of this heteroepitaxial
approach has been development of high quality CdTe buffer layers deposited on Si(112) substrates. We review the solutions
developed by several groups to address the difficulties associated with the CdTe/Si(112) heteroepitaxial system, including
control of crystallographic orientation and minimization of defects such as twins and threading dislocations. The material
quality of HgCdTe/Si and the performance of HgCdTe detector structures grown on CdTe/Si(112) composite substrates is reviewed.
Finally, we discuss some of the challenges related to composition uniformity and defect generation encountered with scaling
the MBE growth process for HgCdTe to large-area Si substrates.
Journal of Electronic Materials 05/1999; 28(6):705-711. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present recent progress on the use of an integrated real-time sensing and control system for monitoring and controlling substrate temperature, layer composition, and effusion cell flux during MBE growth of HgCdTe epilayers for advanced IR detectors. Substrate temperature is measured and controlled in real-time using absorption-edge spectroscopy (ABES). This allows the substrate temperature to be maintained at +/-1.5 deg C from the desired setpoint, even during actuation of effusion cell shutters which under conventional thermocouple-based control would produce a substantial (10-15 deg C) temperature change. In situ spectroscopic ellipsometry (SE) is used for monitoring HgCdTe layer composition in real-time. We describe the development of a comprehensive temperature- and composition-dependent SE dielectric function database which can be used for accurate and precise monitoring of Hg(1-x)Cd(x)Te layer composition over a wide range of x-values, from 0.2 to 0.42. The composition changes inferred from the real-time SE measurements obtained during growth of a two-layer structure are in excellent agreement with actual composition vs. depth profiles obtained using post-growth SIMS analysis. Likewise, 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 gas-phase concentration of Cd atoms produced by a CdTe effusion cell are detected using an atomic absorption method (optical-absorption flux monitoring OFM). The OFM method allows changes in HgCdTe layer composition to be correlated directly with variations in Cd flux. The in situ optical sensors are linked using a custom software framework to provide the foundation for integrated, real-time monitoring and control of HgCdTe MBE growth of high performance IR detector structures over a wide range of compositions, layer thickness and substrate temperature.
07/1998;
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[show abstract]
[hide abstract]
ABSTRACT: Molecular beam epitaxy (MBE) has been utilized to fabricate high performance HgCdTe infrared detectors with sensitivity to midwave infrared radiation in adjacent spectral bands for two-color thermal imaging applications. Growth of a multilayer HgCdTe device structure by MBE enables the use of an n-p-n device architecture that facilitates pixel-level registration of images in two separate spectral bands. Device structures were grown on CdZnTe(211)(B) substrates using CdTe, Te, and Hg sources with in situ In and As doping. The composition of the HgCdTe alloy layers was adjusted to achieve detection of infrared radiation in adjacent spectral bands in the 3.5–4.5 μm wavelength range. As-grown device structures were characterized with x-ray diffraction, wet chemical defect etching, and secondary ion mass spectrometry. Mesa type devices were patterned using reactive ion etching and ohmic contacts were made to the two n -type layers for operation of the detectors in a sequential detection mode. The spectral response characteristics of the devices are highly uniform across a 64×64 element array, with standard deviation in cutoff wavelength less than 0.01 μm and external quantum efficiencies greater than 70% in both bands. Sharp detector cutoffs enable spectral crosstalk less than 1% to be obtained for spectral bands with as little as 0.6 μm separation. Junction reverse-breakdown voltages in excess of 500 mV and 80 K dynamic resistance-area products for each component diode in excess of 1×10<sup>6</sup> Ω cm <sup> 2 </sup> at ±100 mV operating bias have been demonstrated. © 1998 American Vacuum Society.
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 06/1998; · 1.34 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: 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.
Journal of Electronic Materials 05/1998; 27(6):494-499. · 1.47 Impact Factor
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T. J. de Lyon,
R. D. Rajavel,
J. A. Vigil, J. E. Jensen,
O. K. Wu,
C. A. Cockrum,
S. M. Johnson,
G. M. Venzor,
S. L. Bailey,
I. Kasai,
W. L. Ahlgren,
M. S. Smith
[show abstract]
[hide abstract]
ABSTRACT: Molecular beam epitaxy has been employed to deposit HgCdTe infrared detector structures on Si(112) substrates with performance
at 125K that is equivalent to detectors grown on conventional CdZnTe substrates. The detector structures are grown on Si via
CdTe(112)B buffer layers, whose structural properties include x-ray rocking curve full width at half maximum of 63 arc-sec
and near-surface etch pit density of 3–5 × 105 cm−2 for 9 µm thick CdTe films. HgCdTe p+-on-n device structures were grown by molecular beam epitaxy (MBE) on both bulk CdZnTe and Si with 125K cutoff wavelengths
ranging from 3.5 to 5 µm. External quantum efficiencies of 70%, limited only by reflection loss at the uncoated Si-vacuum
interface, were achieved for detectors on Si. The current-voltage (I-V) characteristics of MBE-grown detectors on CdZnTe and
Si were found to be equivalent, with reverse breakdown voltages well in excess of 700 mV. The temperature dependences of the
I-V characteristics of MBE-grown diodes on CdZnTe and Si were found to be essentially identical and in agreement with a diffusion-limited
current model for temperatures down to 110K. The performance of MBE-grown diodes on Si is also equivalent to that of typical
liquid phase epitaxy-grown devices on CdZnTe with R0A products in the 106–107 Θ-cm2 range for 3.6 µm cutoff at 125K and R0A products in the 104–105 Θ-cm2 range for 4.7 µm cutoff at 125K.
Journal of Electronic Materials 05/1998; 27(6):550-555. · 1.47 Impact Factor
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R. D. Rajavel,
D. M. Jamba, J. E. Jensen,
O. K. Wu,
P. D. Brewer,
J. A. Wilson,
J. L. Johnson,
E. A. Patten,
K. Kosai,
J. T. Caulfield,
P. M. Goetz
[show abstract]
[hide abstract]
ABSTRACT: Molecular beam epitaxy was employed for the growth of HgCdTe-based n-p+-n device structures on (211)B oriented CdZnTe substrates. The device structures were processed as mesa isolated diodes, and
operated as back-to-back diodes for the simultaneous detection of two closely spaced sub-bands in the mid-wave infrared spectrum.
The devices were characterized by R0A values in excess of 5 × 105 Ω cm2 at 78K, at f/2 fov and quantum efficiencies greater than 70% in each band. Infrared imagery from a focal plane array with
128 × 128 pixels was acquired simultaneously from each band at temperatures between 77 to 180K, with no observable degradation
in the image quality with increase in temperature.
Journal of Electronic Materials 01/1998; 27(6):747-751. · 1.47 Impact Factor
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R. D. Rajavel,
D. M. Jamba, J. E. Jensen,
O. K. Wu,
C. Le Beau,
J. A. Wilson,
E. Patten,
K. Kosai,
J. Johnson,
J. Rosbeck,
P. Goetz,
S. M. Johnson
[show abstract]
[hide abstract]
ABSTRACT: The first report of molecular beam epitaxial growth and performance of HgCdTe two-color detectors for the simultaneous detection
of radiation at 4.1 and 4.5 μm is presented. In-situ doped devices with the n-p-n architecture were grown by molecular beam
epitaxy on (211)B CdZnTe substrates. Representative structures exhibited x-ray rocking curves with full width at half-maxima
of 40–60 arcs. The typical near surface etch pit density in these structures were 4−7 × 106 cm−2. The devices were processed as mesa diodes and electrical contacts were made to the two n-type layers and the p-type layer
to facilitate simultaneous operation of the two p-n junctions. The spectral response characteristics of the devices were characterized
by sharp turn-on and turn-off for both bands, with R0A values >5 × 105 ωcm2 at 77K. The detectors exhibited quantum efficiencies >70% in both bands.
Journal of Electronic Materials 05/1997; 26(6):476-481. · 1.47 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: High-quality, single-crystal epitaxial films of CdTe(112)B and HgCdTe(112)B have been grown directly on Si(112) substrates
without the need for GaAs interfacial layers. The CdTe and HgCdTe films have been characterized with optical microscopy, x-ray
diffraction, wet chemical defect etching, and secondary ion mass spectrometry. HgCdTe/Si infrared detectors have also been
fabricated and tested. The CdTe(112)B films are highly specular, twin-free, and have x-ray rocking curves as narrow as 72
arc-sec and near-surface etch pit density (EPD) of 2 × 106 cm−2 for 8 µm thick films. HgCdTe(112)B films deposited on Si substrates have x-ray rocking curve FWHM as low as 76 arc-sec and
EPD of 3-22 × 106 cm−2. These MBE-grown epitaxial structures have been used to fabricate the first high-performance HgCdTe IR detectors grown directly
on Si without use of an intermediate GaAs buffer layer. HgCdTe/Si infrared detectors have been fabricated with 40% quantum
efficiency and R0A = 1.64 × 104 Ωm2 (0 FOV) for devices with 7.8 µm cutoff wavelength at 78Kto demonstrate the capability of MBE for growth of large-area HgCdTe
arrays on Si.
Journal of Electronic Materials 07/1996; 25(8):1341-1346. · 1.47 Impact Factor
