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  • 1
    Digitale Medien
    Digitale Medien
    Laser induced oxygen adsorption and intensity degradation of porous Si (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3841-3842 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: For light-emitting porous Si there has been a severe problem with instability and degradation in the light emission. We performed in situ photoluminescence measurements to monitor the degradation process under ambient atmosphere of different gases and in ultrahigh-vacuum environment. We found that laser induced oxygen adsorption is the major cause for the light emission degradation, while the laser heating effect can be excluded. We also found the degraded intensity can be partially recovered by reducing the surface oxygen concentration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352288
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  • 2
    Digitale Medien
    Digitale Medien
    Photoreflectance characterization of AlGaAs/GaAs modulation-doped heterostructures (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2355-2360 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoreflectance (PR) and reflectance have been applied to characterize undoped and modulation-doped heterostructures of AlGaAs/GaAs grown by metal-organic chemical vapor deposition. The PR spectra were taken on these samples after sequential etching steps in a phosphoric acid etch to study the effects of the surface electric field, the heterointerface, and the two-dimensional electron gas. PR spectra were also taken with an external electric field applied through a transparent gate electrode. The results show that the oscillations appearing near the bandgap energy of GaAs are Franz–Keldysh oscillations originating from the large surface electric field. The surface electric field of the heterostructures can be modified through the application of an external electric field or by etching. The oscillation period is observed to increase with increasing reverse bias or with etching of the GaAs cap layer and the PR features disappear at a forward bias of 0.45 V. The very sharp features associated with the GaAs bandgap energy after etching have also been verified to be Franz–Keldysh oscillations and the presence of a two-dimensional electron gas cannot be confirmed with PR.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346544
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  • 3
    Digitale Medien
    Digitale Medien
    Computer correction for distorted STM images (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5649-5652 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In quite a few cases, the geometric distortion of a scanning tunneling microscope (STM) image is essentially caused by the nonorthogonal scanning. A physical and mathematical model is proposed to correct such distortion, giving a satisfactory result.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1143395
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  • 4
    Digitale Medien
    Digitale Medien
    Inverted pseudomorphic high electron mobility heterostructures by atmospheric pressure metalorganic chemical vapor deposition (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 71-73 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Inverted pseudomorphic high electron mobility transistor (HEMT) and inverted HEMT heterostructures are demonstrated by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) for the first time and characterized by transmission electron microscopy (TEM), variable temperature Hall effect, and Shubnikov–de Haas measurements. TEM micrographs of both structures show distinct and sharp heterojunction interfaces without indications of interface roughness at the AlGaAs/channel layer interface. Variable temperature Hall effect measurements reveal a monotonic increase in mobility as the temperature is lowered. For the inverted HEMT, the mobility at 15 K is 90 000 cm2/V s with a sheet density of 8.2×1011 cm−2. The mobility of the inverted pseudomorphic HEMT at 15 K is 73 000 cm2/V s with a sheet density of 1.5×1012 cm−2. Shubnikov–de Haas measurements at 4.2 K in magnetic fields up to 18.5 T show clear magnetoresistance oscillations and plateaus in the quantum Hall effect confirming the existence of a two-dimensional electron gas. Fast Fourier power transform of the magnetoresistance versus magnetic field shows two subband levels with a total sheet density of 8.7×1011 cm−2 for the inverted HEMT and a total sheet density of 1.55×1012 cm−2 for the inverted pseudomorphic HEMT in close agreement to the variable temperature Hall effect measurement results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104448
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  • 5
    Digitale Medien
    Digitale Medien
    Reflectance line shapes from GaAs/Ga1−xAlxAs quantum well structures (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 287-289 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Reflectance experiments on GaAs/Ga1−xAlxAs single quantum well structures were performed at 4.2 K, with different thicknesses of the front GaAlAs barrier layer (100–1000 A(ring)). The observed exciton reflectance line shapes depend strongly on the thickness of the front barrier layer due to the interferences between the reflected waves from the front surface and the quantum well interfaces. Calculations of the reflectance line shapes show good agreement with the observations. The absorption coefficient for the electron heavy-hole exciton transition in a single quantum well sample is determined. Our study also provides a new understanding of the line shapes measured in photoreflectance experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99496
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  • 6
    Digitale Medien
    Digitale Medien
    Growth of pseudomorphic high electron mobility heterostructures by atmospheric pressure metalorganic chemical vapor deposition (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 274-276 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Pseudomorphic high electron mobility heterostructures are demonstrated by atmospheric pressure metalorganic chemical vapor deposition for the first time. Transmission electron microscopy (TEM), variable temperature Hall effect measurements, Shubnikov–de Haas measurements, and photoreflectance were applied to characterize the heterostructures. TEM micrographs of the cross section reveal sharp heterojunction interfaces. Variable temperature Hall effect measurements show a monotonic increase in mobility as the temperature is lowered. With a spacer thickness of 120 A(ring), a peak mobility of 80 000 cm2/V s at 20 K and a sheet carrier concentration of 1.05×1012 cm−2 are obtained. Similarly, a thinner spacer (60 A(ring)) shows a peak mobility of 57 000 cm2/V s at 25 K with a sheet carrier concentration of 1.40×1012 cm−2. Shubnikov–de Haas measurements in magnetic fields up to 18.5 T show clear oscillations and the quantum Hall effect confirming the existence of a two-dimensional electron gas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.102806
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  • 7
    Digitale Medien
    Digitale Medien
    Evidence of room-temperature exciton by magnetophotoreflectance in epitaxial GaAs and quantum well structures (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 984-986 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoreflectance experiments with magnetic fields up to 14.5 T are performed on epitaxial GaAs and GaAs/Ga1−xAlxAs quantum well samples at room temperature and 2 K. Our experiments show unique and direct evidence that photoreflectance structures are excitonic transitions in all of the above cases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99249
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  • 8
    Digitale Medien
    Digitale Medien
    Si delta-doped field-effect transistors by atmospheric pressure metalorganic chemical vapor deposition (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 458-460 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Si delta-doped GaAs field-effect transistors (FETs) are demonstrated by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) and characterized by Hall-effect, capacitance-voltage (C-V), and Shubnikov de-Haas measurements. The Si delta doping was accomplished by interrupting the growth and flowing silane with controlled timing under an arsenic overpressure. Devices with 0.5 μm gate length (Ns=2.2×1012 cm−2) were fabricated with a maximum extrinsic transconductance of 140 mS/mm and a current gain cutoff frequency of 17 GHz. The transconductance as a function of gate voltage showed a plateau region through a range of 1.5 V further supporting spatial confinement of the electrons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105435
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  • 9
    Digitale Medien
    Digitale Medien
    Anomalous temperature dependencies of photoluminescence for visible-light-emitting porous Si (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 986-988 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Porous Si has been prepared by the electrochemical anodization method. At room temperature it has a light-emission peak energy in the range of 1.50–2.06 eV. The results from variable-temperature photoluminescence (PL) show anomalous temperature dependencies of the spectral characteristics: the emission intensity increases with decreasing temperature until reaching an intensity maximum at about 100–200 K, then it decreases at lower temperatures; the emission energy shift with temperature has no fixed trend and varies with sampling point. Such dependencies are reversible with the two directions of temperature change. The above observations can be explained by phonon participation in the light-emission process of porous Si.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.106482
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  • 10
    Digitale Medien
    Digitale Medien
    Photoreflective spectroscopy of doped and undoped Cd"1"-"xMn"xTe
    Amsterdam : Elsevier
    Solid State Communications 66 (1988), S. 351-354 
    Details
    ISSN: 0038-1098
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0038-1098(88)90855-1
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