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  • 1
    Digitale Medien
    Digitale Medien
    Optical gain and laser emission in HgCdTe heterostructures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6908-6915 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A detailed study of stimulated emission mechanisms as well as laser emission capability has been carried out on Hg1−xCdxTe (0.44〈x〈0.5) separate-confinement heterostructures grown by molecular beam epitaxy. At low temperature, spontaneous photoluminescence (PL) occurs on extrinsic levels below the gap whereas optical gain exhibits a maximum of stimulated emission shifted towards higher energy, close to the gap. As temperature increases, spontaneous PL is shifted from the extrinsic states to the band-to-band transition by a thermally activated detrapping of the carriers. Above 100 K, spontaneous and stimulated emission vary in a similar way with temperature. Laser emission has been observed up to room temperature for all the heterostructures. The use of quantum wells in the active layer and graded index in the barriers has allowed a significant reduction of the excitation density threshold, as compared to a single separate-confinement heterostructure (SCH) of same composition. However, the high-temperature characteristic temperature T0 is found to be similar in the two structures. A SCH with a higher energy gap exhibits a more favorable behavior with temperature. These experimental results have been compared to theoretical models. The experimentally observed T0 can be well simulated by taking into account the Auger effect. From the experimental data, the Auger constant has been determined for each heterostructure. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360457
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  • 2
    Digitale Medien
    Digitale Medien
    "New donors'' in silicon: An interface effect due to internal oxidation (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3192-3195 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The analysis of Czochralski-silicon annealed in the range 500–800 °C is performed using infrared transmission, electron paramagnetic resonance and admittance spectroscopy measurements. It is shown that the experimental data and especially, new original data obtained with the pulsed admittance spectroscopy technique are consistent with a new model. The "new donors'' effect would in fact be the result of the inversion layer around silica precipitates. This model is demonstrated taking in account the known properties of the Si/SiO2 interface (between precipitates and the silicon crystal). The electrical conduction is shown to be a percolation process through an inhomogeneously conducting material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.337735
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  • 3
    Digitale Medien
    Digitale Medien
    Spectroscopic study of CdTe layers grown by molecular-beam epitaxy on (001) and (111) Cd0.96Zn0.04Te substrates (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 1338-1346 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The optical properties of CdTe grown by molecular-beam epitaxy are investigated by means of high-resolution photoluminescence, reflectivity, transmission, and resonant excitation spectroscopy. The CdTe epilayers are grown on (001)- and (111) B-oriented Cd0.96Zn0.04Te substrates. Sharp and strong lines associated with impurity bound exciton recombination dominate the spectra and indicate a good crystalline quality as well as a low level of impurity contamination. For the donor bound exciton lines, two electron transitions are observed which allow an identification of the chemical nature of the donors (probably Ga) by comparison with the data previously obtained on bulk material. For the acceptor lines, however, the shallow states which contribute to the spectra are different from those reported in the bulk and seem correlated with more complex centers. This study also reveals the importance of the residual strain contribution. Moreover, the marked difference observed for the optical properties between the (001) and the (111) epilayers spectra clearly evidence the change in the incorporation rate of impurities and/or grown-in defects density with the growth direction. The best spectra are obtained for the (001)-oriented CdTe layers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.344433
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  • 4
    Digitale Medien
    Digitale Medien
    3.2 μm infrared resonant cavity light emitting diode (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2591-2593 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A CdHgTe resonant cavity light emitting diode is proposed as a new infrared emitter. The device consists of a bottom Bragg reflector of 86% reflectivity, a half-wavelength cavity, n doped at the beginning (1018 cm−3) and p doped at the end (1018 cm−3), containing an active layer at the antinode position, and a top gold mirror of 95% reflectivity which also serves as an Ohmic contact. The emission spectrum shows a narrow peak of 8 meV full width at half-maximum (FWHM) at 300 K, which is much less than the inhomogeneous linewidth of CdHgTe quantum wells (QWs). This electroluminescent peak matches very well the cavity resonance wavelength and FWHM, as given by transmission measurements of the unbiased cavity. The directivity is also improved by the cavity effect. Thus, we have demonstrated that even a relatively low Q microcavity can greatly enhance the characteristics of an infrared emitter in the 2–5 μm range. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115141
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  • 5
    Digitale Medien
    Digitale Medien
    Implantation-enhanced interdiffusion of CdTe-ZnTe heterostructures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2524-2534 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Implantation-enhanced interdiffusion of CdTe-ZnTe strained heterostructures is studied by photoluminescence, channeling, transmission electron microscopy, and secondary-ion-mass spectrometry. In the tellurides, implantation defects significantly diffuse and anneal out during implantation, so that only residual extended defects are found, at depths several times greater than the implantation projected range Rp. As a result, interdiffusion is achieved during the implantation, and not during the subsequent annealing which only serves to eliminate the residual defects, thereby restoring the optical properties of the heterostructures. Evidence has been found for trapping of residual defects at the interfaces, perhaps due to strain, and of slower diffusion in multiple quantum wells than in bulk material. These interface-trapped defects are quite hard to anneal out, so that single quantum wells exhibit poor optical properties after implantation and annealing, while multiple quantum wells give rise to nice photoluminescence spectra with sharp blue-shifted lines and appear as promising candidates to realize lateral confinement.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354693
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  • 6
    Digitale Medien
    Digitale Medien
    Luminescence characterization of CdTe:In grown by molecular beam epitaxy (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2651-2653 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on the incorporation of indium as a shallow donor in CdTe by molecular beam epitaxy. Using proper surface stoichiometry conditions, we demonstrate that it is possible to incorporate and activate up to 1018 cm−3 indium impurities. The doped layers have been characterized by secondary-ion mass spectroscopy, capacitance-voltage and Hall-effect measurements. Photoluminescence (PL) and resonant excitation of the PL clearly identify indium as the chemical dopant, acting as an effective mass donor with an energy of 14 meV. Incorrect stoichiometry conditions lead to a poor dopant activity and to complex centers formation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104797
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  • 7
    Digitale Medien
    Digitale Medien
    Molecular beam epitaxy growth and characterization of CdxHg1−xTe (0.4〈x〈1) based quantum wells (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1774-1781 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: CdxHg1−xTe epilayers and CdxHg1−xTe/CdyHg1−yTe quantum well heterostructures have been grown by molecular beam epitaxy. The various parameters of the growth technique have been carefully optimized: control of the thickness by the observation of the oscillations of the reflection-high-energy electron diffraction, the alloy composition by measuring the Cd sticking coefficient in our growth procedure, and the quality of the interfaces by performing transmission electron microscopy. The photoluminescence spectra at 5 K of thick CdxHg1−xTe epilayers are dominated by bound exciton recombination below the fundamental band gap Eg. By contrast, the main emission in the quantum wells photoluminescence spectra is due to an intrinsic recombination of the confined carriers in their respective ground state. The influence of CdxHg1−xTe well thickness and the CdyHg1−yTe barrier composition of this quantum well transition energy are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351213
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  • 8
    Digitale Medien
    Digitale Medien
    Room temperature electro-optic effect in CdHgTe multiple quantum well heterostructures at 1.5 μm (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 856-858 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present a study of the room temperature electromodulation properties of CdHgTe heterostructures as a base component for a photorefractive device operating at 1.5 μm. We reach absorption modulation as high as 200%, in the near-gap transparent region of the spectrum, by application of a reverse bias of the order of 100 kV/cm. We observe the transition from the Franz–Keldysh effect in 200 Å wide wells to the quantum confined Stark effect in 90 Å wells. The calculated diffraction efficiency in a suitable photorefractive device would be of the order of 8×10−4 in both cases. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118297
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  • 9
    Digitale Medien
    Digitale Medien
    Photopumped infrared vertical-cavity surface-emitting laser (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2480-2482 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The feasibility of a photopumped infrared vertical-cavity surface-emitting laser (VCSEL) based on CdHgTe alloys is demonstrated. The structure of the VCSEL consists of a 16.5-period Cd0.4Hg0.6Te/Cd0.75Hg0.25Te bottom Bragg reflector and a 3λ/4 thick Cd0.75Hg0.25Te cavity, containing a 100-nm-thick well, grown by molecular beam epitaxy. The top mirror is a 7-period YF3/ZnS dielectric stack. The cavity quality factor is Q=350. This heterostructure VCSEL operates at 3.06 μm with a measured power density threshold of 45 kW/cm2 at 10 K. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115827
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  • 10
    Digitale Medien
    Digitale Medien
    Nonlinear interdiffusion in semiconductor superlattices: Case of CdTe/HgTe (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2548-2550 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Experiments have been designed to measure the interdiffusion coefficients in CdTe/HgTe (001) superlattices grown by molecular beam epitaxy. The interdiffusion coefficients are deduced from double-crystal x-ray diffraction on samples annealed in the 200–240 °C range under a Hg saturated pressure. Our results indicate that the interdiffusion is strongly dependent on concentration with a coefficient given by D(CCd,T)=1.0 exp{[−1.45(±0.1) eV]/(kT)} exp {[−0.55 (±0.1) CCd eV]/(kT)} cm2/s. The activation energies ΔEHgTe≈1.45 eV and ΔECdTe≈2.0 eV are consistent with an interdiffusion process by a vacancy mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.109292
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