共查询到20条相似文献,搜索用时 31 毫秒
1.
M. S. Han T. W. Kang J. H. Leem B. K. Song Y. B. Hou W. H. Baek M. H. Lee J. H. Bahng K. J. Kim J. M. Kim H. K. Kim T. W. Kim 《Journal of Electronic Materials》1997,26(6):507-510
Spectroscopic ellipsometry and photoreflectance measurements on CdTe/GaAs strained heterostructures grown by moleculclr beam
epitaxy were carried out to investigate the effect of the strain and the dependence of the lattice parameter on the CdTe epitaxial
layer thicknesses. Compressive strains exist in CdTe layers thinner than 2 μm. As the strain increases, the value of the critical-point
energy shift increases linearly. These results indicate that the strains in the CdTe layers grown on GaAs substrates are strongly
dependent on the CdTe layer thickness.
Author to whom all correspondence should be addressed. 相似文献
2.
In this paper, we report on the atomic layer epitaxy (ALE) of CdTe on GaAs and Si by the organometallic vapor phase epitaxial
process at atmospheric pressure. Self-limiting growth at one monolayer was obtained over the temperature range from 250°C
to 320°C, under a wide range of reactant pressure conditions. A study of growth mechanism indicates that DMCd decomposes into
Cd on the surface and the Te precursors react catalytically on the Cd covered surface. We have used this ALE grown layer to
improve the crystal quality and the morphology of conventionally grown CdTe on GaAs. Improvement in the crystal quality was
also observed when ALE CdTe nucleation was carried out on Si pretreated with DETe at 420°C. Atomic layer epitaxy grown ZnTe
was used to obtain (100) oriented CdTe on (100) silicon. 相似文献
3.
High quality Al0.28Ga0.72As0.62P0.38 layers were grown on GaAso.6iPo.39 epitaxial sub-strates by liquid-phase epitaxy using a supercooling technique. The electrical
properties of the AlGaAsP layers were determined by capacitance-voltage measurements at 300K. The undoped layers always give
n-type conduction with a background concentration of 1 × 1016 cm−3. The 9-K photoluminescence spectra show three distinctive peaks and their relative intensities change with the excitation
power density. The temperature dependence of photoluminescence from the undoped AlGaAsP layers shows that there is a new peak
emerging above 30K. The four major emission peaks have been identified, involving intrinsic recombination, donor-to-valence-band
transitions, conduction-band-to-acceptor transitions, and donor-acceptor pair transitions. The binding energies of the residual
donors and acceptors are 13.7 and 36 meV, respectively, nevertheless these impurites are not completely identified. 相似文献
4.
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
5.
S. S. You B. Rodricks S. Sivananthan J. P. Faurie P. A. Montano 《Journal of Electronic Materials》1996,25(8):1306-1311
We have been fabricating x-ray photoconductor linear array detectors using molecular beam epitaxially (MBE) grown (lll)B undoped
CdTe layers on (100) Si substrates. A novel technique was developed to remove the Si and to mount the fragile MBE grown CdTe
layers onto insulating ceramic substrates. 256 channel linear photoconductor array devices were fabricated on the resulting
CdTe layers. The resistivity of MBE (lll)B CdTe was high (>108 \cm) enough to utilize the material for low energy (8 ~ 25
keV) x-ray detectors. The stability of the detectors are satisfactory, and they were tested at room temperature routinely
for over a year. The performance of the photoconductor was greatly improved when the detector was cooled to 230K. Due to its
reduced dark current at low temperatures, the dynamic range of the detector response increased to nearly four decades at 230K. 相似文献
6.
M. Niraula K. Yasuda T. Ishiguro Y. Kawauchi H. Morishita Y. Agata 《Journal of Electronic Materials》2003,32(7):728-732
The growth characteristics and crystalline quality of thick (100) CdTe-epitaxial layers grown on (100) GaAs and (100) GaAs/Si
substrates in a metal-organic vapor-phase epitaxy (MOVPE) system for possible applications in x-ray imaging detectors were
investigated. High-crystalline-quality epitaxial layers of thickness greater than 100 μm could be readily obtained on both
types of substrates. The full width at half maximum (FWHM) values of the x-ray double-crystal rocking curve (DCRC) decreased
rapidly with increasing layer thickness, and remained around 50–70 arcsec for layers thicker than 30 μm on both types of substrates.
Photoluminescence (PL) measurement showed high-intensity excitonic emission with very small defect-related peaks from both
types of epilayers. Stress analysis carried out by performing PL as a function of layer thickness showed the layers were strained
and a small amount of residual stress, compressive in CdTe/GaAs and tensile in CdTe/GaAs/Si, remained even in the thick layers.
Furthermore, the resistivity of the layers on the GaAs substrate was found to be lower than that of layers on GaAs/Si possibly
because of the difference of the activation of incorporated impurity from the substrates because of the different kinds of
stress existing on them. A heterojunction diode was then fabricated by growing a CdTe epilayer on an n+-GaAs substrate, which exhibited a good rectification property with a low value of reverse-bias leakage current even at high
applied biases. 相似文献
7.
Theory of te precipitation and related effects in CdTe Crystals 总被引:1,自引:0,他引:1
A thermodynamic calculation is presented which explains the origin of often reported large stress fields in and around Te
precipitates and associated punching of dislocation loops in star like patterns. The calculation is based on the consideration
that the stoichiometric deviation in Te saturated crystals are accommodated by Te interstitials, Cd multivacancy complexes
and Te antisites; the Te interstitials are most mobile of them, and dominate the precipitation process; and the precipitates
when they appear first are in droplet form. The droplet state is modelled on the basis of the Lennard-Jones 6-12 interaction
potential. The droplet growth is envisaged to occur via the following two processes operating in tandem: first, capture of
excess Te interstitials to cause droplet overpressurization, and then, punching of interstitial dislocation loops whenever
the pressure exceeds a threshold value. The flow of Te interstitials into the droplets is driven by the difference between
their formation energies in the lattice and the free energy change of the droplets per Te atom added. It is shown that the
achievable droplet pressures far exceed that required for the loop punching and sustaining the growth cycle. The occurrence
of varying precipitate morphologies are explained, and the possibility of nucleating high presssure Te phases is examined.
Some experimental evidence is also presented which corroborate the theoretical arguments involved. 相似文献
8.
W. Palosz K. Grasza P. R. Boyd Y. Cui G. Wright U. N. Roy A. Burger 《Journal of Electronic Materials》2003,32(7):747-751
High-quality CdTe crystals with resistivities higher than 108 Ω cm were grown by the physical-vapor transport (PVT) technique. Indium, aluminum, and the transition-metal scandium were
introduced at the nominal level of about 6 ppm to the source material. Low-temperature photoluminescence (PL) has been employed
to identify the origins of PL emissions of the crystals. The emission peaks at 1.584 eV and 1.581 eV were found only in the
In-doped crystal. The result suggests that the luminescence line at 1.584 eV is associated with Cd-vacancy/In complex. The
intensity of the broadband centered at 1.43 eV decreases strongly with introduction of Sc. 相似文献
9.
We discuss various possibilities for determining the orientation of CdTe layers grown on (001) GaAs and in particular, determining
the (001) orientation. This growth orientation is characterized by a three dimensional growth mechanism which controls the
growth in the (111) orientation. We show that a thin layer of ZnTe deposited directly on the oxide free GaAs surface can be
used to determine the (001) orientation, eliminate (111) phases and enhance a two dimensional growth of the CdTe layer, resulting
in an improved crystalline quality and a smooth surface morphology. CdTe layers grown in the (111) direction on oxide free
(001) GaAs substrates contain (111) microtwins and an intermixed (001) phase.
This work is a part of a Ph.D. thesis to be submitted to the Weizmann Institute of Science. 相似文献
10.
Q. Jiang A. W. Brinkman B. J. Cantwell J. T. Mullins Fabrice Dierre A. Basu P. Veeramani P. Sellin 《Journal of Electronic Materials》2009,38(8):1548-1553
This paper reports on a detailed study of the development of the close space sublimation method, which has been widely used
in the preparation of polycrystalline CdTe/CdS solar cells, as an epitaxial method for the growth of thick CdTe single crystal
films over 200 μm on GaAs and Ge substrates for high-energy radiation detectors. The resulting microscopic growth phenomena in the process
are also discussed in this paper. High-quality single crystalline CdTe thick films were prepared with x-ray rocking curves
full width at half maximum (FWHM) values, which were ∼100 arcsec on Ge substrates and 300 arcsec on GaAs substrates. The quality
of thick films on Ge(100) showed a substantial improvement with nucleation in a Te-rich growth environment. No Te inclusions
in the CdTe films grown on GaAs(211)B and Ge(100) were observed with IR transmission imaging. Photoluminescence of CdTe/Ge
shows a large reduction in the 1.44 eV defect energy bands compared with films grown on GaAs substrates. The film resistivity
is on the order of 1010 Ω cm, and the film displayed some sensitivity to alpha particles. 相似文献
11.
M. S. Han S. R. Hahn H. C. Kwon Y. Bin T. W. Kang J. H. Leem Y. B. Hou H. C. Jeon J. K. Hyun Y. T. Jeoung H. K. Kim J. M. Kim T. W. Kim 《Journal of Electronic Materials》1998,27(6):680-683
Double-crystal x-ray rocking curve (DCRC) and secondary-ion mass-spectroscopy (SIMS) measurements have been performed to investigate the effect of rapid thermal annealing on the interdiffusion behavior of Hg in HgTe/CdTe superlattices grown on Cd0.96Zn0.04Te (211)B substrates by molecular beam epitaxy. The sharp satellite peaks of the DCRC measurements on a 100-period HgTe/CdTe (100Å/100Å) superlattice show a periodic arrangement of the superlattice with high-quality interfaces. The negative direction of the entropy change obtained from the diffusion coefficients as a function of the reciprocal of the temperature after RTA indicates that the Hg diffusion for the annealed HgTe/CdTe superlattice is caused by an interstitial mechanism. The Cd and the Hg concentration profiles near the annealed HgTe/CdTe superlattice interfaces, as measured by SIMS, show a nonlinear behavior for Hg, originating from the interstitial diffusion mechanism of the Hg composition. These results indicate that a nonlinear interdiffusion behavior is dominant for HgTe/CdTe superlattices annealed at 190°C and that the rectangular shape of HgTe/CdTe superlattices may change to a parabolic shape because of the intermixing of Hg and Cd due to the thermal treatment. 相似文献
12.
M. Milanova A. Mintairov V. Rumyantsev K. Smekalin 《Journal of Electronic Materials》1999,28(1):35-38
This paper describes the spectral characteristics of GaAs solar cells grown by low-temperature liquid phase epitaxy (LPE). It demonstrates improvements in blue response and peak internal quantum efficiencies of 100 percent for an optimized cell structure with isovalent In doped base and ultrathin (<100Å) heavily doped cap p+-GaAs layer on the photosensitive surface. The conversion efficiency obtained from the optimized cells under one-sun AM 1.5 conditions is 23.4 percent. Our results indicate that the low-cost LPE-grown films are suitable for high-efficiency solar cells. 相似文献
13.
Y. P. Chen J. P. Faurie S. Sivananthan G. C. Hua N. Otsuka 《Journal of Electronic Materials》1995,24(5):475-481
CdTe(lll)B layers have been grown on misoriented Si(001). Twin formation inside CdTe(lll)B layer is very sensitive to the
substrate tilt direction. When Si(001) is tilted toward [110] or [100], a fully twinned layer is obtained. When Si(001) is
tilted toward a direction significantly away from [110], a twin-free layer is obtained. Microtwins inside the CdTe(111)B layers
are overwhelmingly dominated by the lamellar twins. CdTe(111)B layers always start with heavily lamellar twinning. For twin-free
layers, the lamellar twins are gradually suppressed and give way to twin-free CdTe(111)B layer. The major driving forces for
suppressing the lamellar twinning are the preferential orientation of CdTe[11-2] along Si[1-10] and lattice relaxation. Such
preferential orientation is found to exist for the CdTe(111)B layers grown on Si(001) tilted toward a direction between [110]
and [100]. 相似文献
14.
15.
The self-diffusion of Cd and Te in liquid phase epitaxially grown CdTe layers has been studied using stable isotopes of Cd108 and Te122. A two layer structure was grown from In solutions at 300–250° C, with the first layer being normal CdTe and the second enriched
in Cd108 and Te122. Secondary ion mass spectrometry was used to measure the concentration of the Cd and Te species as a function of depth in
the as-grown structure and after heat treatment at 500° C. The main result was that after heating, no movement of Te could
be detected. However, the Cd had diffused rapidly both at the solidsolid epilayer interface and at the solid-vapour interface.
The self-diffusion coefficient for Cd in CdTe calculated from this data was D500°
cd ˜ 3 ± 1 × 1013cm2s-1 in reasonable agreement with published data. 相似文献
16.
Microstructural and optical characterization of CdTe(211)B/ZnTe/Si(211) grown by molecular beam epitaxy 总被引:2,自引:0,他引:2
S. Rujirawat David J. Smith J. P. Faurie G. Neu V. Nathan S. Sivananthan 《Journal of Electronic Materials》1998,27(9):1047-1052
CdTe layers have been grown by molecular beam epitaxy on 3 inch nominal Si(211) under various conditions to study the effect
of growth parameters on the structural quality. The microstructure of several samples was investigated by high resolution
transmission electron microscopy (HRTEM). The orientation of the CdTe layers was affected strongly by the ZnTe buffer deposition
temperature. Both single domain CdTe(133)B and CdTe(211)B were obtained by selective growth of ZnTe buffer layers at different
temperatures. We demonstrated that thin ZnTe buffer layers (<2 nm) are sufficient to maintain the (211) orientation. CdTe
deposited at ∼300°C grows with its normal lattice parameter from the onset of growth, demonstrating the effective strain accommodation
of the buffer layer. The low tilt angle (<1°) between CdTe[211] and Si[211] indicates that high miscut Si(211) substrates
are unnecessary. From low temperature photoluminescence, it is shown that Cd-substituted Li is the main residual impurity
in the CdTe layer. In addition, deep emission bands are attributed to the presence of AsTe and AgCd acceptors. There is no evidence that copper plays a role in the impurity contamination of the samples. 相似文献
17.
N. C. Giles Jaesun Lee T. H. Myers Zhonghai Yu B. K. Wagner R. G. Benz C. J. Summers 《Journal of Electronic Materials》1995,24(5):691-696
A comprehensive study of the properties of undoped and iodine-doped CdTe structures by photoluminescence (PL) and photoreflectance
(PR) is reported. Undoped bulk CdTe and iodine-doped CdTe layers grown by metalorganic molecular beam epitaxy on (lOO)-oriented
CdTe and (211)B-oriented GaAs substrates with electron concentrations ranging from 1014 to mid-1018 cm-3 were included in this study. Lineshape modeling of 80KPL and PR spectra indicated the presence of both free exciton and donor-hole
transitions at the higher doping levels. Strong PL and PR signals were also observed at room temperature. If only a single
transition is considered for the analysis of the 300K spectra, the PL emission peak and the PR transition energy both exhibit
a strong dependence on electron concentration for doped layers. However, lineshape modeling of the room-temperature spectra
indicated the presence of multiple transitions consisting of free exciton and direct band-to-band transitions. The use of
two transitions resulted in a constant value of bandgap over the entire range of conductivities studied. A strong correlation
remained between the broadening of the PR and PL spectra and excess carrier concentration ND-NA. In addition, the E1 transition energy measured by PR was found to vary dramatically with growth conditions. 相似文献
18.
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
19.
We have performed selective area epitaxy (SAE) of CdTe layers grown by molecular beam epitaxy using a shadow mask technique.
This technique was chosen over other SAE techniques due to its simplicity and its compatibility with multiple SAE patterning
steps. Features as small as 50 microns × 50 microns were obtained with sharp, abrupt side walls and flat mesa tops. Separations
between mesas as small as 20 microns were also obtained. Shadowing effects due to the finite thickness of the mask were reduced
by placing the CdTe source in a near normal incidence position. Intimate contact between the mask and the substrate was essential
in order to achieve good pattern definition. 相似文献
20.
A. Abul-Fadl E. Stefanakos W. Nance W. Collis J. McPherson 《Journal of Electronic Materials》1980,9(3):621-638
It is the purpose of this paper to investigate the suitability and effectiveness of growth of thin GaAs layers on polycrystalline GaAs substrates by liquid phase epitaxy (LPE) and current controlled LPE (CCLPE). During each growth run LPE and CCLPE were used to grow thin GaAs layers on two large-grain polycrystalline GaAs substrates cut from the same wafer and simultaneously placed in the same growth system. The grain boundary was exposed by cleaving the samples perpendicular to the grain boundary. Notnarski contrast, SEM, C-V and Hall measurements were performed in order to determine the surface morphology, discontinuity of epilayer at the grain boundary, epilayer thickness unform-ity, resistivity (in directions parallel and perpendicular to the grain boundary), and dopant concentration. The CCLPE system was carefully designed so that growth would take place only by electrotransport in the absence of convection or Peltier cooling. The results indicate that CCLPE yields layers with improved surface morphology and thickness uniformity as compared to those grown by LPE. In some samples the epilayer was discontinuous at certain grain boundaries. Results are presented on CCLPE growth rate dependence upon grain orientation, current density, and continuity of the epilayer at the grain boundary. 相似文献