共查询到20条相似文献,搜索用时 15 毫秒
1.
Jacobs R. N. Stoltz A. J. Robinson E. W. Boyd P. R. Almeida L. A. Dinan J. H. Salamanca-Riba L. 《Journal of Electronic Materials》2004,33(6):538-542
The vision of achieving a completely in-vacuum process for fabricating HgCdTe detector arrays is contingent on the availability
of a vacuumcompatible photolithography technology. One such technology for vacuum photolithography involves the use of amorphous-hydrogenated
Si (a-Si:H) as a photoresist. In this work, we deposit a-Si:H resists via plasma-enhanced chemical-vapor deposition (PECVD)
using an Ar-diluted silane precursor. The resists are then patterned via excimer laser exposure and development etched in
a hydrogen plasma where etch selectivities between unexposed and exposed regions exceed 600:1. To determine the best conditions
for the technique, we investigate the effects of different exposure environments and carry out an analysis of the a-Si:H surfaces
before and after development etching. Analysis via transmission electron microscopy (TEM) reveals that the excimer-exposed
surfaces are polycrystalline in nature, indicating that the mechanism for pattern generation in this study is based on melting
and crystallization. To demonstrate pattern transfer, underlying CdTe films were etched (after development of the resist)
in an electron cyclotron resonance (ECR) plasma, where etch selectivities of approximately 8:1 have been achieved. The significance
of this work is the demonstration of laser-induced poly-Si as an etching mask for vacuum-compatible photolithography. 相似文献
2.
R. N. Jacobs E. W. Robinson M. Jaime-Vasquez A. J. Stoltz J. Markunas L. A. Almeida P. R. Boyd J. H. Dinan L. Salamanca-Riba 《Journal of Electronic Materials》2006,35(6):1474-1480
A vacuum-compatible process for carrying out lithography on Hg1−xCdxTe and CdTe films was previously demonstrated. It was shown that hydrogenated amorphous silicon (a-Si:H) could be used as
a dry resist by projecting a pattern onto its surface using excimer laser irradiation and then developing that pattern by
hydrogen plasma etching. Pattern transfer to an underlying Hg1−xCdxTe film was then carried out via Ar/H2 plasma etching in an electron cyclotron resonance (ECR) reactor. Despite the successful demonstration of pattern transfer,
the possibility of inducing harmful effects in the Hg1−xCdxTe film due to this vacuum lithography procedure had not been explored. Here we present structural and surface compositional
analyses of Hg1−xCdxTe films at key stages of the a-Si:H vacuum lithography procedure. X-ray diffraction double crystal rocking curves taken before
and after a-Si:H deposition and after development etching were identical, indicating that bulk structural changes in the Hg1−xCdxTe film are not induced by these processes. Cross-section transmission electron microscopy studies show that laser-induced
heating in the 350 nm thick a-Si:H overlayer is not sufficient to cause structural damage in the underlying Hg1−xCdxTe surface. In vacuo surface analysis via Auger electron spectroscopy and ion scattering spectroscopy suggest that the hydrogen
plasma development process produces Hg-deficient surfaces but does not introduce C contamination. However, after ECR plasma
etching into the Hg1−xCdxTe film, the measured x value is much closer to that of the bulk. 相似文献
3.
E. P. G. Smith C. A. Musca D. A. Redfern J. M. Dell L. Faraone 《Journal of Electronic Materials》2000,29(6):853-858
An experimental study has been carried out on the performance of n-type x = 0.31 HgCdTe photoconductive detectors in order
to evaluate two different etching techniques; dry plasma etching, in the form of H2/CH4 reactive ion etching (RIE), and wet chemical etching using bromine in hydrobromic acid. Two-dimensional laser beam-induced
current (LBIC) imaging was employed as an in-line process monitoring tool to evaluate the lateral extent of reactive ion etching
(RIE) induced doping changes in the HgCdTe epilayer following mesa delineation. Responsivity and noise measurements were performed
on fabricated mid-wavelength infrared (MWIR) photoconductive devices to evaluate the influence dry plasma etching has on material
properties. For a signal wavelength of 3 μm, 60° field of view, and a temperature of 80 K, background limited D
λ
*
performance was recorded for wet chemical processed devices but not for the dry plasma processed devices. The D
λ
*
values obtained for wet chemical and dry plasma etched photoconductive detectors were 2.5×1011 cmHz1/2W−1 and 1.0×1010 cmHz1/2W−1, respectively. Mercury annealing, which has been shown to restore the electrical properties of dry plasma processed HgCdTe,
could be used to lessen the influence that RIE dry plasma etching has on photoconductor detector performance. 相似文献
4.
Changzhen Wang Steve Tobin Themis Parodos David J. Smith 《Journal of Electronic Materials》2006,35(6):1192-1196
The microstructure of p-n device structures grown by liquid-phase epitaxy (LPE) on CdZnTe substrates has been evaluated using
transmission electron microscopy (TEM). The devices consisted of thick (∼21-μm) n-type layers and thin (∼1.6-μm) p-type layers,
with final CdTe (∼0.5 μm) passivation layers. Initial observations revealed small defects, both within the n-type layer (doped
with 8×1014/cm3 of In) and also within the p-type layer but at a much reduced level. These defects were not visible, however, in cross-sectional
samples prepared by ion milling with the sample held at liquid nitrogen temperature. Only isolated growth defects were observed
in samples having low indium doping levels (2×1014/cm3). The CdTe passivation layers were generally columnar and polycrystalline, and interfaces with the p-type HgCdTe layers were
uneven. No obvious structural changes were apparent in the region of the CdTe/HgCdTe interfaces as a result of annealing at
250°C. 相似文献
5.
Lijie Zhao J. S. Speck R. Rajavel J. Jensen D. Leonard T. Strand W. Hamilton 《Journal of Electronic Materials》2000,29(6):732-735
Transmission electron microscopy (TEM) was used to evaluate the microstructure of molecular beam epitaxy (MBE) grown (211)B
oriented HgCdTe films. TEM analysis of in-situ doped p-on-n and n-p-n device structures will be presented. Under fully optimized
growth conditions the substrate-epilayer interface is free of threading dislocations and twins, and a high degree of structural
integrity is retained throughout the entire device structure. However, under non-optimal growth conditions that employ high
Hg/Te flux ratios, twins can be generated in the p-type layer of p-on-n device structure, resulting in roughness and facetting
of the film surface. We propose a mechanism for twin formation that is associated with surface facetting. TEM evaluation of
voids, threading dislocations and Te-precipitates in HgCdTe films are also discussed. 相似文献
6.
V. Kumar R. Pal P. K. Chaudhury B. L. Sharma V. Gopal 《Journal of Electronic Materials》2005,34(9):1225-1229
Passivant-Hg1−xCdxTe interface has been studied for the CdTe and anodic oxide (AO) passivants. The former passivation process yields five times
lower surface recombination velocity than the latter process. Temperature dependence of surface recombination velocity of
the CdTe/n-HgCdTe and AO/n-HgCdTe interface is analyzed. Activation energy of the surface traps for CdTe and AO-passivated
wafers are estimated to be in the range of 7–10 meV. These levels are understood to be arising from Hg vacancies at the HgCdTe
surface. Fixed charge density for CdTe/n-HgCdTe interface measured by CV technique is 5×1010 cm−2, which is comparable to the epitaxially grown CdTe films. An order of magnitude improvement in responsivity and a factor
of 4 increase in specific detectivity (D*) is achieved by CdTe passivation over AO passivation. This study has been conducted
on photoconductive detectors to qualify the CdTe passivation process, with an ultimate aim to use it for the passivation of
p-on-n and n-on-p HgCdTe photodiodes. 相似文献
7.
Inductively coupled plasmas (ICP) are the high-density plasmas of choice for the processing of HgCdTe and related compounds.
Most dry plasma process works have been performed on HgCdTe for pixel delineation and the p-to-n-type conversion of HgCdTe. We would like to use the advantages of “dry” plasma processing to perform passivation etching
of HgCdTe. Plasma processing promises the ability to create small vias, 2 μm or less with excellent uniformity across a wafer, good run-to-run uniformity, and good etch rate control. In this study
we developed processes to controllably etch CdTe, the most common passivation material used for photovoltaic-based HgCdTe
devices. We created a process based on xenon gas that allows for the slow controllable CdTe etch at only 0.035 μm/min, with smooth morphology and rounded corners to promote further processing. 相似文献
8.
J. White R. Pal J. M. Dell C. A. Musca J. Antoszewski L. Faraone P. Burke 《Journal of Electronic Materials》2001,30(6):762-767
The role of hydrogen incorporation in H2/CH4 reactive ion etching (RIE) induced type-conversion of p-type HgCdTe is investigated. A model is proposed in which hydrogen
is incorporated into the HgCdTe crystal lattice in at least three different forms. It is proposed that the junction formation
mechanism is a mixture of RIE-induced damage and Hg interstitial formation to which hydrogen forms strong bonds, and hydrogen-induced
neutralization of acceptors. Confirmation of the model is presented based on experimental secondary ion mass spectroscopy
of RIE-induced junctions, transport measurements reported previously, and initial diode bake stability testing. 相似文献
9.
T. J. De Lyon G. L. Olson J. A. Roth J. E. Jensen A. T. Hunter M. D. Jack S. L. Bailey 《Journal of Electronic Materials》2002,31(7):688-693
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. 相似文献
10.
We report on a new, simple process to fabricate planar Hg1−yCdyTe/Hg1−xCdxTe (x<y) heterostructure photodiodes with p-on-n configuration. The material used for this demonstration was a double-layer
p-on-n heterostructure that was grown by a liquid-phase-epitaxy technique. The p-on-n planar devices consisted of an arsenic-doped
p-type epilayer (y=0.28) on top of a long-wavelength infrared n-type epilayer (x=0.225, =10 m). The ion-beam-milling p-type
to n-type conversion effect was used to delineate the active device element, and to isolate the planar device. Detailed analysis
of the current-voltage characteristics of these diodes as a function of temperature show that they have high performance,
and that their dark current is diffusion-limited down to 60 K. The results show that over a wide range of cut-off wavelengths,
the R0A product values are close to the theoretical limit. Electro-optic properties of a 2-D array of small diodes with a 60- m
pitch are presented, and demonstrate the potential of the new process for implementation of 2-D arrays. The electrical properties
of the photodiodes are stable following long-term annealing at 80°C for 48 hours. 相似文献
11.
J. B. Varesi J. D. Benson M. Martinka A. J. Stoltz W. E. Mason L. A. Almeida A. W. Kaleczyc P. R. Boyd J. H. Dinan 《Journal of Electronic Materials》2005,34(6):758-761
We have examined the etching of HgCdTe (x=0.2) with bromine/ethylene glycol (Br/EG) solutions. Using a spectroscopic ellipsometer,
we tracked the ellipsometric parameters (ψ and Δ) of the freshly etched HgCdTe surfaces. Parameters ψ and Δ were measured
periodically as these values changed with the surface exposed to air. A second set of Br/EG-etched samples was stored in deionized
(DI) water. We found that DI water effectively preserved the freshly etched HgCdTe surface for a period of several hours.
Comparison with the literature on HgCdTe surface chemistry implies that oxide growth is inhibited on the etched HgCdTe samples
immersed in DI water. Modeling results based on the measured ψ and Δ values agree with this assessment. 相似文献
12.
Progress in MOVPE of HgCdTe for advanced infrared detectors 总被引:1,自引:0,他引:1
This paper reviews the significant progress made over the past five years in the development of metalorganic vapor phase epitaxy
(MOVPE) for the in situ growth of HgCdTe p-n junction devices for infrared detector arrays. The two basic approaches for MOVPE growth of HgCdTe,
the interdiffused multilayer process (IMP), and direct alloy growth (DAG) are compared. The paper then focuses on the progress
achieved with the IMP approach on lattice-matched CdZnTe substrates. The benefits of the precursors ethyl iodide (EI) and
tris-dimethylaminoarsenic (DMAAs) for controlled iodine donor doping and arsenic acceptor doping at dopant concentrations relevant
for HgCdTe junction devices are summarized along with the electrical and lifetime properties of n-type and p-type HgCdTe films
grown with these precursors. The relative merits of the two CdZnTe substrate orientations we have used, the (211)B and the
(100) with 4°–8° misorientation are compared, and the reasons why the (211)B is preferred are discussed. The growth and repeatability
results, based on secondary ion mass spectrometry analysis, are reported for a series of double-heterojunction p-n-N-P dual-band
HgCdTe films for simultaneous detection in the 3–5 μm and 8–10 μm wavelength bands. Finally, the device characteristics of
MOVPE-IMP in situ grown p-on-n heterojunction detectors operating in the 8–12 μm band are reviewed and compared with state-of-the-art liquid
phase epitaxial grown devices. 相似文献
13.
Molecular beam epitaxial HgCdTe material characteristics and device performance: Reproducibility status 总被引:1,自引:0,他引:1
J. Bajaj J. M. Arias M. Zandian J. G. Pasko L. J. Kozlowski R. E. De Wames W. E. Tennant 《Journal of Electronic Materials》1995,24(9):1067-1076
Extensive material, device, and focal plane array (FPA) reproducibility data are presented to demonstrate significant advances
made in the molecular beam epitaxial (MBE) HgCdTe technology. Excellent control of the composition, growth rate, layer thickness,
doping concentration, dislocation density, and transport characteristics has been demonstrated. A change in the bandgap is
readily achieved by adjusting the beam fluxes, demonstrating the flexibility of MBE in responding to the needs of infrared
detection applications in various spectral bands. High performance of photodiodes fabricated on MBE HgCdTe layers reflects
on the overall quality of the grown material. The photodiodes were planar p-on-n junctions fabricated by As ion-implantation
into indium doped, n-type, in situ grown double layer heterostructures. At 77K, diodes fabricated on MBE Hg1−xCdxTe with x ≈ 0.30 (λco
≈ 5.6 μm), x ≈ 0.26 (λco
≈ 7 μm), x ≈ 0.23 (λco ≈ 10 μm) show R0A products in excess of 1 x 106 ohm-cm2, 7 x 105 ohm-cm2, and 3 x 102 ohm-cm2, respectively. These devices also show high quantum efficiency. As a means to assess the uniformity of the MBE HgCdTe material,
two-dimensional 64 x 64 and 128 x 128 mosaic detector arrays were hybridized to Si multiplexers. These focal plane arrays
show an operability as high as 97% at 77K for the x ≈ 0.23 spectral band and 93% at 77K for the x ≈ 0.26 spectral band. The
operability is limited partly by the density of void-type defects that are present in the MBE grown layers and are easily
identified under an optical microscope. 相似文献
14.
S. K. Jha P. Srivastava R. Pal Anjali H. K. Sehgal Hee Chul Lee O. P. Agnihotri B. B. Gong 《Journal of Electronic Materials》2003,32(8):899-905
Mercury cadmium telluride (Hg1?xCdxTe or MCT) has been commonly used in devices for infrared (IR) detection. For the optimum performance of the device, a compatible surface-passivation technology that provides long-term stability is required. Using x-ray photoelectron spectroscopy (XPS), the present study examines the effects on Hg0.8Cd0.2Te passivated with CdTe and ZnS undergoing baking in vacuum at temperatures typically used for dewar bakeout. Spectra recorded as a function of depth in both cases clearly show out-diffusion of Hg from the substrate toward the surface, even before the bakeout. On baking in vacuum, dramatic changes are observed in the ZnS/MCT case with complete loss of Hg from the sample up to the tested depth of more than 1,000 Å. Compositions of the HgCdTe matrix, formed after Hg out-diffusion, before and after the bakeout are also calculated at selected depths (from 250 Å to 700 Å), which is vital information from a device point of view, as it affects the bandgap of this narrow-band semiconductor. 相似文献
15.
Owen K. Wu Rajesh D. Rajavel Terry J. De Lyon John E. Jensen Mike D. Jack Ken Kosai George R. Chapman Sanghamitra Sen Bonnie A. Baumgratz Bobby Walker Bill Johnson 《Journal of Electronic Materials》1997,26(6):488-492
HgCdTe is an attractive material for room-temperature avalanche photodetectors (APDs) operated at 1.3–1.6 μm wavelengths for
fiber optical communication applications because of its bandgap tunability and the resonant enhancement of hole impact ionization
for CdTe fractions near 0.73. The HgCdTe based separate absorption and multiplication avalanche photodetector is designed
and fabricated for backside illumination through a CdZnTe substrate. The multi-layer device structure is comprised of seven
layers including 1). n
+ contact 2). n
− diffusion buffer 3). n
− absorber 4). n charge sheet 5). n
− avalanche gain 6). p to form junction, and 7).p
+ contact. Several wafers were processed into 45 μm × 45 μm and 100 (μm × 100 μm devices. The mean value of avalanche voltage
is 63.7 V measured at room temperature. At 1 GHz, the device shows a gain of about 7 for a gain-bandwidth product of 7 GHz.
This first demonstration of an all molecular beam epitaxially grown HgCdTe multi-layer heterojunction structure on CdZnTe
substrates represents a significant advance toward the goal of producing reliable room temperature HgCdTe high speed, low
noise avalanche photodetectors. 相似文献
16.
S. Krishnamurthy M. A. Berding Z. G. Yu C. H. Swartz T. H. Myers D. D. Edwall R. DeWames 《Journal of Electronic Materials》2005,34(6):873-879
We calculate the radiative, Auger, and the Shockley-Read-Hall recombination rates with Fermi-Dirac statistics and accurate
band structures to explain the measured temperature dependence and doping dependence of minority carrier lifetimes in three
n- and one p-type sample. We show that a trap state tracking the conduction band edge with very small activation energy can
explain the lifetimes in the n-doped samples considered here. Similarly, for moderately p-doped HgCdTe alloy, a trap level
at 75 meV is needed to explain the observed lifetimes. In either case, movement of Fermi level with respect to the trap level
explains the temperature dependence of the lifetimes. 相似文献
17.
18.
We report on the effects of back channel etch depth and etchant chemistry on the electrical characteristics of inverted staggered advanced amorphous silicon thin-film transistors. We found that the optimum amorphous silicon film thickness in the channel is about 800-1100 Å. Three dry etch, HBr + Cl2, C2F6, and CCl2F2 + O2, and one wet etch, KOH, chemistries are used for the back channel etch processing. We established that dry etch can be used for the back channel etch of amorphous silicon transistor without degrading its electrical characteristics. 相似文献
19.
20.
讨论了 HgCdTe 薄片当其厚度在20μm 左右时,表面与体内导电性质不同所出现的ρ-T 关系曲线,并与正常情况下的ρ-T 关系曲线比较。解释了某些 HgCdTe 薄片电阻率反常的原因。 相似文献