共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
M. A. Folkard G. Shen V. Kumar T. A. Steele D. Rees I. K. Varga D. Carr K. Fueloep B. A. Johnson P. J. Orders R. H. Hartley H. Buskes M. Gal 《Journal of Electronic Materials》1993,22(8):1097-1102
Phase modulated ellipsometric data recorded during molecular beam epitaxial growth of CdTe/HgTe and CdTe/ZnTe superlattices
on (100) and (211)B oriented Cd0.96Zn0.04Te and GaAs substrates are presented. The measurements provide a continuous monitor of the growth process, thickness, growth
rate, compositional data, and evidence of interdiffusion in CdTe/HgTe superlattices at elevated temperatures. The thickness
measurements are independent of growth kinetics and surface orientation and agree well with those obtained from x-ray diffraction
and reflection high energy electron diffraction. Ellipsometry shows that the incorporation of Hg in CdTe is significantly
higher on (100) oriented surfaces than on (211)B oriented surfaces. Fine structure in the data from CdTe/ZnTe superlattices
may be associated with a surface reconstruction during deposition of each CdTe layer. The experimental results for CdTe/HgTe
superlattices compare well with results of thin film multi-layer calculations. The general applicability of ellipsometry as
an in-situ analytical technique for epitaxial growth of a range of semiconductor superlattices is discussed. 相似文献
3.
Y. Selamet Y. D. Zhou J. Zhao Y. Chang C. R. Becker R. Ashokan C. H. Grein S. Sivananthan 《Journal of Electronic Materials》2004,33(6):503-508
High-quality HgTe/CdTe superlattices (SLs) and device structures incorporating them were grown by molecular beam epitaxy (MBE)
on CdTe/Si substrates. In-situ techniques, such as reflection, high-energy electron diffraction and spectroscopic ellipsometry,
were extensively used to rigorously control the growth parameters. The full width at half maximum (FWHM) of x-ray double-crystal
rocking curves (DCRCs) were 100–150 arcsec, comparable to those of HgCdTe alloys grown on the same type of substrates. The
room-temperature Fourier transform infrared (FTIR) spectrum exhibits two-dimensional features characteristic of SLs. Trial
devices in a p+-n−-n+ format were fabricated by diffusing gold in order to further evaluate the HgTe/CdTe SL performance. Gold diffusion was chosen
to fabricate photovoltaic junctions in order to preserve the structural integrity of the SLs during the device processing.
Though no attempt was made in the current study to optimize the junction properties by Au diffusion, this method has proven
to be very useful for rapid preliminary evaluation. The measured spectral-response and detectivity data indicate the possibility
to fabricate photovoltaic devices on an HgTe/CdTe SL, although further work is needed to optimize the p-n junction fabrication. 相似文献
4.
HgTe/CdTe superlattices (SL) have been studied for applications involving the detection of very-long wavelength infrared (VLWIR)
detectors. In this study, p-type HgTe/CdTe SLs were grown by molecular beam epitaxy (MBE). As-grown arsenic δ-doped HgTe/CdTe
SLs and undoped HgTe/CdTe SLs were characterized before and after annealing under different conditions using XRD, temperature-dependent
Hall-effect measurements, SIMS, and TEM. Incorporated arsenic atoms in a HgTe/CdTe SL were electrically activated without
the typical thermal annealing of alloy HgCdTe materials. 相似文献
5.
Robert C. Keller M. Seelmann-Eggebert H. J. Richter 《Journal of Electronic Materials》1995,24(9):1155-1160
We report on several new aspects of etching of Hg1−xCdxTe (x = 0.22), HgTe, and CdTe in CH4/H2/Ar plasmas generated by an electron cyclotron resonance plasma source. Using a residual gas analyzer, we have identified
elemental Hg, TeH2, Te(CH3)2, and Cd(CH3)2 as the primary reaction products escaping from a HgCdTe surface during the plasma exposure. We have also demonstrated that
a bias is not needed to etch HgCdTe at moderate temperatures (30-40°C), as previously suggested by other researchers. We have
also developed a technique that avoids the formation of hydrocarbon polymer films on a HgCdTe sample during etching. Moreover,
we have examined by x-ray photoelectron spectroscopy analysis and ellipsometry the surface condition of HgCdTe resulting from
etching with this technique at zero bias. After exposure to the CH4/H2Ar plasma (or to a H2/Ar plasma only), the HgCdTe samples exhibited a depletion of the HgTe component in the near surface region (increase of the
x-value). The depletion covered a range from virtually x = 1 after H2/Ar (10:2 in sccm) etching to values 0.4 < x < 0.5 after CH4/H2Ar (7:7:2 in seem) etching. Exposures to the plasmas were found to result in surface roughening of HgCdTe, however, plasmas
rich in H2 were observed to cause significantly rougher surfaces than plasmas with small H2/CH4 ratios. This difference in the resulting surface condition is attributed solely to chemical effects since the respective
ion energies are considered to be below the damage threshold for HgCdTe in both cases. We also investigated the etching of
HgTe and CdTe single crystals. The etch rate of HgTe was found to be over one order of magnitude higher than that of CdTe
under similar conditions. This large difference in etch rates is assumed to be responsible for the observed preferential etching
of the HgTe component indicated by the HgTe depletion of the HgCdTe surface region. 相似文献
6.
L. S. Hirsch R. Haakenaasen T. Colin K. S. Ziemer C. D. Stinespring S. Lovold T. H. Myers 《Journal of Electronic Materials》1999,28(6):810-816
X-ray photoelectron spectroscopy has been used to study the low-temperature (<80°C) preparation of HgCdTe surfaces with atomic hydrogen for the purpose of CdTe passivation. Atomic hydrogen was used to etch overlayers and surfaces of liquid phase epitaxy and molecular beam epitaxy HgCdTe, CdTe, HgTe, and Te. Oxide layers were easily removed, while carbon overlayers were resistant to atomic hydrogen etching at low temperature. Both Te and HgTe are etched by atomic hydrogen, with the HgTe etch rate about twice that of Te, while CdTe and ZnTe are not etched. Chemi-mechanical polishing of liquid phase epitaxy HgCdTe left a 10 to 20Å Te overlayer that could be removed with atomic hydrogen. In all cases, exposure of HgCdTe to atomic hydrogen led to surface composition shifts to higher x-value, with an x-value plateau near x~0.6. All observations could be explained in terms of the formation of a 15Å surface layer of CdTe which blocks further etching. 相似文献
7.
Zhonghai Yu M. A. Mattson T. H. Myers K. A. Harris R. W. Yanka L. M. Mohnkern L. C. Lew Yan Voon L. R. Ram-Mohan R. G. Benz B. K. Wagner C. J. SummersBenz 《Journal of Electronic Materials》1995,24(5):685-690
Epitaxial growth of Hg-based semiconductors by molecular beam epitaxy (MBE) and metalorganic MBE (MOMBE) has progressed sufficiently
to shift emphasis to the control of factors limiting the yield of both materials and devices. This paper reports on anex-situ study to evaluate the suitability of reflectance and photoreflectance (PR) asin-situ characterization techniques for the growth of CdTe and HgCdTe. Photoreflectance yields information about CdTe layers, with
largest utility for doped and multi-layer structures. However, caution must be taken in interpretation of the spectra since
the near-bandedge PR spectra consists of multiple transitions and the E1 transition energy is very sensitive to the sample history. Photoreflectance appears to be of limited utility for HgCdTe single
layer growth with x<0.4. However, reflectance measurements of the E1 peak can be used to determine composition in HgCdTe single layers with an accuracy Δx = ±0.01, which can be useful for growth
control. A tight binding model was used to calculate the E1 peak energy as a function of bandgap for HgCdTe and HgTe/CdTe superlattices. Comparisons are made with experimental observations.
Surface interdiffusion in HgTe-CdTe superlattices was probed using reflectance measurements. 相似文献
8.
R. W. Vanka K. A. Harris L. M. Mohnkern A. R. Reisinger T. H. Myers N. Otsuka 《Journal of Electronic Materials》1993,22(8):1107-1112
Two material properties important to the application of HgTe/CdTe superlattices for device fabrication are band gap uniformity
and thermal stability. In this paper, we present the results of an infrared photoluminescence study of (211)B HgTe/CdTe superlattices
grown by photon-assisted molecular beam epitaxy which show that cut-off wavelength uniformity can be controlled to a level
commensurate with the demands of advanced infrared detector fabrication. Infrared photoluminescence and transmission electron
microscopy were also employed to demonstrate that (211)B HgTe/CdTe superlattices are less prone to interdiffusion than previously
believed. 相似文献
9.
R. Sizmann P. Helgesen T. Colin T. Skauli S. Løvold 《Journal of Electronic Materials》1996,25(3):497-500
The use of a magnetic field for interband absorption experiments in the midinfrared regime can reveal the electronic band
structure of HgTe/CdTe superlattices. In high-quality samples pronounced magnetic field-induced absorption peaks are observed
in the transmission spectra due to hole to electron Landau level transitions. By extrapolating the excitation energies for
such transitions to B = 0, gap energies between several hole and electron subbands can be determined accurately. In addition,
we show that interband magnetoabsorption provides a sensitive feedback for growth of quantum structures. 相似文献
10.
The type III band alignment of HgTe/CdTe superlattices leads to the interesting possibility of achieving very long wavelength
infrared (VLWIR) (15 μm and longer) cutoff wavelengths with either normal (HgTe layer thickness less than about 70 ? for CdTe
layer thickness of 50 ?) or inverted (HgTe thickness greater than about 70 ?) band structures. The inverted band structure
superlattices promise even greater cutoff wavelength control than the normal band structure ones. However, the electronic
band gaps of inverted band structure superlattices are substantially less than their optical band gaps, leading to large thermal
carrier concentrations even at temperature as low as 40 K. These high carrier concentrations in turn give rise to more rapid
Auger recombination than normal band structure superlattices with the same cutoff wavelengths. We conclude that the highest
performance is expected from VLWIR HgTe/CdTe superlattice-based detectors with normal band structure absorber layers. 相似文献
11.
Philip Klipstein 《Journal of Electronic Materials》2018,47(10):5719-5724
HgTe/CdTe and InAs/GaSb/AlSb superlattices both exhibit a topological insulator transition. In each case, there is an inversion of the s- and p-band ordering for layer thicknesses above a critical value. The resulting topological phase is a 2D bulk insulator at zero temperature, with edges that conduct massless carriers whose direction of motion is locked to their direction of spin. These 1D edge states exhibit essentially dissipationless transport over coherence lengths greater than one micron, with a quantized conductance of e2/h per edge. When a current passes, opposite spins are separated to the two sample edges, giving rise to the so-called quantum spin Hall effect. Effects such as these may be exploited in future low temperature spintronic devices. The edge states in HgTe/CdTe differ from those in InAs/GaSb/AlSb in several ways, due to the type II band alignment and weaker electron–hole hybridization of the III-V superlattice. The former exhibit a simple exponential decay over thousands of Angstroms, while the latter are more strongly confined to the edge, with an oscillating wave function whose period increases with the edge state momentum. In any calculation, the edge state dispersion and the nature of the wave-function depend strongly on the boundary conditions used. A k · p model is presented using standard boundary conditions for the wave function and its derivative, which yields spin polarized edge states with a finite amplitude at the sample edge. The interaction between states at opposite sample edges is also considered. 相似文献
12.
M. A. Mattson T. H. Myers M. Richards-Babb J. R. Meyer 《Journal of Electronic Materials》1997,26(6):578-583
We show that variations of the E1 reflectance peak in Hg-based superlattices can be used to probe low-temperature interdiffusion by monitoring the shift of
the E1 peak with time over extended periods. Little evidence of interdiffusion was detected for a number of HgTe/CdTe and HgCdTe/CdTe
superlattices stored at room temperature for approximately two years. Two HgTe/CdTe superlattices and one HgCdTe/CdTe superlattice
were subsequently annealed in a dry nitrogen atmosphere at 100°C for approximately six months, and then at 150°C for 24 days.
During these intervals, the superlattices were periodically removed from the anneal for reflectance measurements to assess
the extent of the interdiffusion. Comparison of these results with calculations of superlattice bandgaps and interdiffusion
profiles has led to an evaluation of the low temperature interdiffusion coefficients. These extend previous results to lower
temperatures and confirm that the degradation of Hg-based superlattices devices due to thermal interdiffusion under normal
processing, storage, and operating conditions should not be an issue of concern. 相似文献
13.
The dynamic mass-loss technique has been employed to measure Hg partial pressures over Te-saturated Hg1-xCdxTe solid solutions with x = 0.40, 0.54, and 0.70 in the 10-1 to 10-4 atm range. The relative chemical potentials of HgTe in Hg1-xCdxTe solid solutions have been calculated using the measured Hg partial pressures at temperatures below 413°C, and fitted into
an analytical expression. A Gibbs-Duhem integration yielded the relative chemical potentials of CdTe. By combining the relative
chemical potentials of the binary components HgTe and CdTe, an expression for the Gibbs free energy of mixing was derived.
The binodal (miscibility gap) and spinodal curves of the Hg1-xCdxTe solid solutions have been established with the critical temperature and composition of 221°C and Hg0.40Cd0.60Te. 相似文献
14.
Using the molecular beam epitaxial (MBE) technique, CdTe and Hg1-xCdxTe have been grown on Cr-doped GaAs (100) sub-strates. A single effusion cell charged with polycrystal-line CdTe is used for the growth of CdTe films. The CdTe films grown at 200 °C with a growth rate of ~ 2 μm/hr show both streaked and “Kikuchi” patterns, indicating single crystalline CdTe films are smoothly grown on the GaAs sub-strates. A sharp emission peak is observed at near band-edge (7865 Å, 1.577 eV) in the photoluminescence spectrum at 77 K. For the growth of Hg1-xCdxTe films, separate sources of HgTe, Cd and Te are used. Hg0.6Cd0.4Te films are grown at 50 °C with a growth rate of 1.7 μm/hr. The surfaces are mirror-smooth and the interfaces between the films and the substrates are very flat and smooth. As-grown Hg0.6Cd0.4Te films are p-type and converted into n-type by annealing in Hg pressure. Carrier concentration and Hall mobility of an annealed Hg0.6Cd0.4Te film are 1 × 1017 cm?3 and 1000 cm2/V-sec at 77 K, respectively. 相似文献
15.
The permittivity spectra ε1(E) and ε2(E) of ZnSe and CdTe crystals are calculated in the range of 10–25 eV using their experimental reflectance spectra and Kramers–Kronig integral relations. The spectra are decomposed into thirteen and twelve separate transition bands for ZnSe and CdTe, respectively, using the improved nonparametric combined Argand diagram technique. The main spectral parameters, including the maximum energies and halfwidths and oscillator strengths, are determined. The oscillator strengths are found to be within 0.1–1.4 for ZnSe and 0.2–0.7 for CdTe. The obtained ε2(E) bands are due to interband and exciton transitions with the involvement of cation core d bands of both crystals under consideration. 相似文献
16.
J. W. Park Jaesun Lee Y. M. Moon J. B. Choi M. S. Hahn B. K. Song Y. B. Hou T. W. Kang Kyung-Hwa Yoo C. A. Hoffman J. R. Meyer Y. T. Jeoung H. K. Kim J. M. Kim 《Journal of Electronic Materials》1997,26(6):584-587
We report transport results for molecular beam epitaxially grown HgTe/CdTe superlattices (SLs) with CdTe barrier thickness of Lb systematically varied from 100Å down to 20Å, and demonstrate the increasing intersubband mixing between adjacent layers with decreasing Lb. Magnetotransport data measured at 1.5K and for B up to 10T show monotonously varying features with Lb, implying a dimensional change from 2D to quasi-3D. As Lb decreases, the quantum Hall plateaus become weaker and the number of effective 2D channels are decreased, which indicates increasing growth-direction energy dispersion. This enhanced interlayer subband coupling with decreasing Lb is further confirmed by the angle-dependence of SdH oscillations. For Lb = 20Å, all of 2D-related transport behavior are washed out. A quantitative analysis with calculated subband energy dispersion relations demonstrates the close interplay between superlattice barrier thickness and the strength of the intersubband mixing. These transport results are directly related to successful control of the growth-axis carrier effective mass and will contribute to the development of high-performance HgTe/CdTe SL-based IR photo-voltaic devices and lasers, in which tunneling noise due to diffusion currents can be considerably reduced. 相似文献
17.
Emmanuel Lhuillier Sean Keuleyan Heng Liu Philippe Guyot-Sionnest 《Journal of Electronic Materials》2012,41(10):2725-2729
We report on HgTe colloidal-based quantum-dot mid-infrared (IR) photodetectors. We demonstrate tuning the cutoff wavelength of this detector from the near IR up to 7?μm. Responsivity values of films of HgTe nanoparticles a few hundred nanometers thick are in the 100?mA?W?1 range even at room temperature. The detectivity of this film is limited by large 1/f noise. Time responses as short as 200?ns are achieved. 相似文献
18.
Y. Chang C. H. Grein C. R. Becker X. J. Wang Q. Duan S. Ghosh P. Dreiske R. Bommena J. Zhao M. Carmody F. Aqariden S. Sivananthan 《Journal of Electronic Materials》2011,40(8):1854-1859
CdZnTe-based heterojunction p?Ci?Cn or M?C???Cn detectors using HgTe/HgCdTe superlattice contacts are modeled and designed to reduce leakage currents under high electric fields and thereby improve x-ray and ??-ray detector performance. The employment of an n-type HgTe/HgCdTe superlattice as a contact layer can theoretically result in significantly less leakage current compared with a contact layer using either bulk semiconductor or metal contacts. The benefits arise from the ability to design HgTe/HgCdTe superlattices to have large carrier effective masses in the electric field direction, which results in low carrier velocities. Nevertheless the density of states is lower than that of a comparable bulk semiconductor, which results in low carrier concentrations. 相似文献
19.
The surface growth kinetics of CdTe and HgTe have been investigated during molecular and metalorganic molecular beam epitaxy.
The surface growth kinetics was studied through in-situ measurements of the growth rate as a function of flux ratio and substrate
temperature on the (001), (111)B, and (211)B CdTe surface orientations. For the (001) and (111)B CdTe growth kinetics, the
existence of low binding energy surface precursor sites was proposed for both molecular and atomic growth species before lattice
incorporation. Intensity oscillations were observed during HgTe growth on misoriented (111)B surfaces and during CdTe growth
on the (211)B orientation. The (211)B surface reconstructions displayed both vicinal and singular surface characteristics,
depending on the growth flux ratio. 相似文献
20.
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