共查询到10条相似文献,搜索用时 62 毫秒
1.
MBE growth and characterization of in situ arsenic doped HgCdTe 总被引:2,自引:0,他引:2
A. C. Chen M. Zandian D. D. Edwall R. E. De Wames P. S. Wijewarnasuriya J. M. Arias S. Sivananthan M. Berding A. Sher 《Journal of Electronic Materials》1998,27(6):595-599
We report the results of in situ arsenic doping by molecular beam epitaxy using an elemental arsenic source. Single Hg1−xCdxTe layers of x ∼0.3 were grown at a lower growth temperature of 175°C to increase the arsenic incorporation into the layers.
Layers grown at 175°C have shown typical etch pit densities of 2E6 with achievable densities as low as 7E4cm−2. Void defect densities can routinely be achieved at levels below 1000 cm−2. Double crystal x-ray diffraction rocking curves exhibit typical full width at half-maximum values of 23 arcsec indicating
high structural quality. Arsenic incorporation into the HgCdTe layers was confirmed using secondary ion mass spectrometry.
Isothermal annealing of HgCdTe:As layers at temperatures of either 436 or 300°C results in activation of the arsenic at concentrations
ranging from 2E16 to 2E18 cm−3. Theoretical fits to variable temperature Hall measurements indicate that layers are not compensated, with near 100% activation
after isothermal anneals at 436 or 300°C. Arsenic activation energies and 77K minority carrier lifetime measurements are consistent
with published literature values. SIMS analyses of annealed arsenic doping profiles confirm a low arsenic diffusion coefficient. 相似文献
2.
Arsenic incorporation during MBE growth of HgCdTe 总被引:2,自引:0,他引:2
We discuss the equilibrium model of the amphoteric behavior of arsenic in HgCdTe and its applicability to material grown by
molecular beam epitaxy. Suggestions are made on how to achieve active incorporation by manipulating the surface orientation,
or by using precursors that provide steric hindrance. 相似文献
3.
This paper describes our progress to improve the material quality, reproducibility, and flexibility of molecular beam epitaxial
(MBE) growth of HgCdTe. Data, statistics, and yields according to defined screen criteria are presented for n-type layer carrier
concentration and mobility, void defect density, and dislocation density for more than 100 layers. Minority carrier lifetime
data are also presented. Continued improvements in impurity reductiont have allowed us to achieve, for the first time, reproducible,
low n-type carrier concentration in the mid-1014 cnr−3 range with high electron mobility. Data are presented that show that low dislocation density films are obtained for growth
on CdZnTe substrates with a wide range of Zn concentration. Results are presented from a nine-growth run first pass success
demonstration run to further assess material quality reproducibility and flexibility of wavelength band tuning. These results
demonstrate the promising potential of MBE growth for flexible manufacturing of HgCdTe for infrared focal plane arrays. 相似文献
4.
Characterization of CdTe for HgCdTe surface passivation 总被引:2,自引:0,他引:2
L. O. Bubulac W. E. Tennant J. Bajaj J. Sheng R. Brigham A. H. B. Vanderwyck M. Zandian W. V. Mc Levige 《Journal of Electronic Materials》1995,24(9):1175-1182
The objectives of this work are to study the physical and chemical structure of CdTe films using secondary ion mass spectrometry
(SIMS) and atomic force miroscopy (AFM) and to demonstrate the usefulness of these analytical techniques in determining the
characteristics of CdTe-passivation films deposited by different techniques on HgCdTe material. Three key aspects of CdTe
passivation of HgCdTe are addressed by different analytical tools: a) morphological microstructure of CdTe films examined
by atomic force microscopy; b) compositional profile across the interface determined by Matrix (Te)—SIMS technique; c) concentration
of various impurities across the CdTe/HgCdTe structure profiled by secondary ion-mass spectrometry. 相似文献
5.
VSWIR to VLWIR MBE grown HgCdTe material and detectors for remote sensing applications 总被引:1,自引:0,他引:1
A. I. D’souza L. C. Dawson E. J. Anderson A. D. Markum W. E. Tennant L. O. Bubulac M. Zandian J. G. Pasko W. V. McLevige D. D. Edwall J. W. Derr J. E. Jandik 《Journal of Electronic Materials》1997,26(6):656-661
The molecular beam epitaxy (MBE) growth technology is inherently flexible in its ability to change the Hg1−xCdxTe material’s bandgap within a growth run and from growth run to growth run. This bandgap engineering flexibility permits
tailoring the device architecture to the various specific requirements. Material with active layer x values ranging from ∼0.198
to 0.570 have been grown and processed into detectors. This wide range in x values is perfectly suited for remote sensing
applications, specifically the National Polar Orbiting Environmental Satellite System (NPOESS) program that requires imaging
in a multitude of infrared spectral bands, ranging from the 1.58 to 1.64 μm VSWIR (very short wave infrared) band to the 11.5
to 12.5 μm LWIR (longwave infrared) band and beyond. These diverse spectral bands require high performance detectors, operating
at two temperatures; detectors for the VSWIR band operate near room temperature while the SWIR, MWIR (mid wave infra red),
LWIR and VLWIR (very long wave infrared) detectors operate near 100K, because of constraints imposed by the cooler for the
NPOESS program. This paper uses material parameters to calculate theoretical detector performance for a range of x values.
This theoretical detector performance is compared with median measured detector optical and electrical data. Measured detector
optical and electrical data, combined with noise model estimates of ROIC performance are used to calculate signal to noise
ratio (SNR), for each spectral band. The SNR are compared with respect to the meteorological NPOESS system derived focal plane.
The derived system focal plane requirements for NPOESS are met in all the spectral bands. 相似文献
6.
A. Parikh S.D. Pearson B.K. Wagner C.J. Summers 《Journal of Electronic Materials》1997,26(9):1065-1069
A study is reported of the dynamics of dopant incorporation in iodine doped CdTe. Using a mathematical formulation, the iodine
doping profiles in CdTe and HgCdTe have been fitted to experiment to obtain material parameters such as the bulk and surface
diffusion and the segregation energy. Dopant profile fitting showed that iodine diffusion was insignificant and gave an iodine
segregation energy of 0.6 eV and a surface diffusivity enhancement factor of 300 at a growth temperature of 230°C. The model
was used to determine the effect of the growth rate and temperature for particular growth conditions. 相似文献
7.
We have constructed an optical microscopy system to automatically locate, count, and determine the size of polycrystalline
“void” defects on epitaxial layers of HgCdTe grown on CdZnTe or Si substrates. Void macrodefects are readily imaged because
their polycrystalline surface is rough, and consequently they scatter light out of the image under specular reflection imaging
conditions. Using a computer-controlled stage to move the wafer, a succession of individual, contiguous bright-field images
is recorded over the entire wafer. Each image is analyzed by software to locate and characterize all the light-scattering
objects present in the frame. Several different representations of the spatial distribution and size of defects are generated,
and these can be presented either as false-color density maps or dot-location maps. In addition, various types of statistics
on the defect population and size distributions are also available. These data not only convey overall information on the
quality of a given wafer, and as such are quite useful for screening to determine which wafers are suitable for array fabrication,
but they also allow inferences to be made concerning the origin or root cause of different classes of defects. Several examples
are presented to illustrate the use of full-wafer defect mapping to identify macrodefect problems in HgCdTe growth on CdZnTe
that can arise from substrate temperature lateral nonuniformity, nonmatched source flux angular distributions, substrate contamination,
and intrinsic substrate imperfections. 相似文献
8.
Brett Z. Nosho John A. Roth John E. Jensen Le Pham 《Journal of Electronic Materials》2005,34(6):779-785
The fabrication of high-quality focal plane arrays from HgCdTe layers grown by molecular beam epitaxy (MBE) requires a high
degree of lateral uniformity in material properties such as the alloy composition, doping concentration, and defect density.
While it is well known that MBE source flux nonuniformity can lead to radial compositional variation for rotating substrates,
we have also found that composition can be affected significantly by lateral variations in substrate temperature during growth.
In diagnostic experiments, we systematically varied the substrate temperature during MBE and quantified the dependence of
HgCdTe alloy composition on substrate temperature. Based on these results, we developed a methodology to quickly and nondestructively
characterize MBE-grown layers using postgrowth spatial mapping of the cutoff wavelength from the Fourier transform infrared
(FTIR) transmission at 300 K, and we were able to obtain a quantitative relationship between the measured spatial variations
in cutoff and the substrate temperature lateral distribution during growth. We refined this methodology by more directly inferring
the substrate temperature distribution from secondary ion mass spectroscopy (SIMS) measurements of the As concentration across
a wafer, using the fact that the As incorporation rate in MBE-grown p-type layers is highly sensitive to substrate temperature.
Combining this multiple-point SIMS analysis with FTIR spatial mapping, we demonstrate how the relative contributions from
flux nonuniformity and temperature variations on the lateral composition uniformity can be separated. This capability to accurately
map the lateral variations in the substrate temperature has been valuable in optimizing the mounting and bonding of large
substrates for MBE growth, and can also be valuable for other aspects of MBE process development. 相似文献
9.
Measurement of minority carrier lifetime in n-type MBE HgCdTe and its dependence on annealing 总被引:1,自引:0,他引:1
D. D. Edwall R. E. DeWames W. V. McLevige J. G. Pasko J. M. Arias 《Journal of Electronic Materials》1998,27(6):698-702
Results are presented for minority carrier lifetime in n-type molecular beam epitaxy Hg1−xCdxTe with x ranging from 0.2 to 0.6. It was found that the lifetime was unintentionally degraded by post-growth annealing under
Hg saturated conditions in a H2 atmosphere that was both time and temperature dependent. This effect was minimal or non-existent for x∼0.2 material, but
very strong for x ≥ 0.3. Hydrogen was identified as responsible for this degradation. Identical annealing in a He atmosphere
avoids this degradation and results in neartheoretical lifetime values for carrier concentrations as low 1 × 1015 cm−3 in ≥0.3 material. Modeling was carried out for x∼0.2 and x∼0.4 material that shows the extent to which lifetime is reduced
by Shockley-Real-Hall recombination for carrier concentrations below 1 × 1015 cm−3, as well as for layers annealed in H2. It appears that annealing in H2 results in a deep recombination center in wider bandgap HgCdTe that lowers the lifetime without affecting the majority carrier
concentration and mobility. 相似文献
10.
D. D. Edwall D. B. Young A. C. Chen M. Zandian J. M. Arias Brian Dlugosch Scott Priddy 《Journal of Electronic Materials》1999,28(6):740-742
Initial results using a valved Te source for molecular beam epitaxial growth of Hg1−xCdxTe are described. Unlike the case for a conventional Knudsen effusion cell where the flux is controlled primarily by temperature,
flux from the valved source is controlled primarily by a variable orifice capable of good closure so that the cell temperature
can be fixed at the operating temperature. Operating characteristics of the source are described, and include being able to
nearly instantaneously change the flux magnitude at will. Using the source for HgCdTe growth has resulted in promising composition
reproducibility improvement in initial growth runs. 相似文献