摘要:

Iron is nitrided by pulsed excimer laser treatment under liquid ammonia. Conversion electron Mo¨ssbauer spectroscopy and small‐angle x‐ray diffraction measurements reveal formation of &ggr;‐austenite in the as‐treated sample and its transformation to &ggr;’‐Fe4N upon thermal annealing.

ISSN:0003-6951    

DOI:10.1063/1.97702

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Metalorganic vapor phase epitaxy of InP prepared by a trimethylindium‐trimethylphosphine (TMIn‐TMP) adduct and PH3was first grown in a low pressure vertical reactor. The adduct with its irreplaceable merit of high stability has been successfully used in this study. The lowest carrier concentration of undoped InP epilayers is 5×1014cm−3with a 77 K mobility of 75 000 cm2/V s. The full width at half‐maximum of the 77 K photoluminescence spectrum was as narrow as 10 meV. These results can compete with all previous data from adduct sources. The growth rate was not limited by the relatively low vapor pressure of the TMIn‐TMP adduct and could reach to 8 &mgr;m/h. It suggests the high growth efficiency of this growing process.

ISSN:0003-6951    

DOI:10.1063/1.97703

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We report current versus voltage measurements as a function of temperature (I‐V‐T) and capacitance‐voltage (C‐V) measurements onn+‐GaAs/insulator/n‐GaAs capacitors where the insulators used are (i) AlAs and (ii) a GaAs:AlAs superlattice. For then+‐GaAs/AlAs/n‐GaAs structures activation energies of 0.38 eV are observed over the temperature range 100–300 K indicating that conduction takes place by thermionic emission through theX‐band states of AlAs. For the superlattice case a measured activation energy of ∼0.33 eV for thermionic emission has a contribution of ∼0.2 eV resulting from the band bending in the superlattice, as revealed by ourC‐Vmeasurements. We discuss the implications of these results for transport in superlattices and as a technique for determining miniband energies.

ISSN:0003-6951    

DOI:10.1063/1.97704

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new Raman line was found on ultrahigh AlAs‐GaAs superlattices with an excitation energy near the band gap. The excitation profile revealed that the intensity of the new line was enhanced resonantly as well as those of the AlAs‐ and GaAs‐like phonon lines as the excitation photon energy approached the photoluminescence peak energy. Polarization measurements showed that the enhanced lines were induced by the Fro¨hlich mechanism. The normal coordinate treatment of the lattice vibration indicates that these lines can probably be attributed to the longitudinal optical phonons of theEspecies.

ISSN:0003-6951    

DOI:10.1063/1.97705

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have achieved a high responsivity,R=1.9 A/W, 10 &mgr;m infrared detector using intersubband absorption in GaAs/AlxGa1−xAs quantum well superlattices. The photocurrent is produced by intersubband absorption followed by efficient photoexcited tunneling. This responsivity is nearly four times higher than our previous results and has been obtained by using thicker and higher AlxGa1−xAs superlattice barriers thereby reducing the dark current and allowing the detector to be operated at higher biases.

ISSN:0003-6951    

DOI:10.1063/1.97706

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Intermixing of AlxGa1−xAs/GaAs superlattices is demonstrated utilizing laser pulses of a few nanosecond duration. Raman spectroscopy and sputter Auger profiling have been used to assess the degree of intermixing and residual damage in the laser irradiated samples. The results indicate that irradiating with the spatially uniform beam of the excimer laser generates a completely intermixed alloy with no detected residual damage. A thermal melting model is used to qualitatively describe the results.

ISSN:0003-6951    

DOI:10.1063/1.97707

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A photoluminescence study of ZnSe‐ZnSxSe1−xstrained‐layer superlattices withx=0.19 grown by molecular beam epitaxy is presented. We observe clear shifts of the excitons to higher energies as the well widths are reduced. These shifts are interpreted in terms of quantum confinement effects using the envelope function approach and the strain‐induced effects using the deformation potential theory. From our analysis we conclude that most of the band offsets between ZnSe‐ZnSxSe1−xare taken up by the valence bands.

ISSN:0003-6951    

DOI:10.1063/1.97708

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The intermixing of AlAs‐GaAs superlattices has been investigated as a function of Si concentration following anneals in the range of 500 to 900 °C. The superlattice samples were grown by molecular beam epitaxy and the near surface layers were doped with silicon at concentrations of 2×1017to 5×1018cm−3. Si and Al depth profiles were measured with secondary ion mass spectrometry (SIMS). The diffusion length and activation energy of Al as a function of silicon dopant concentration were derived from the SIMS data. In the temperature range studied a single activation energy for the Al diffusion of ∼4 eV was observed, and the Al diffusion coefficients increased rapidly with Si concentration.

ISSN:0003-6951    

DOI:10.1063/1.97709

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Modulation‐doped GaAs heterostructures with low‐temperature electron mobilities of 5.0×106cm2/V s at a two‐dimensional electron areal density of 1.6×1011cm−2have been made. The mobilities are the highest ever observed in a semiconductor. Multiple quantum wells of GaAs prepared by similar methods showed electron mobilities up to 0.54×106cm2/V s at an areal density of 5.3×1011cm−2per layer, which also exceeds any mobility value previously reported for multiple well structures. The structures were grown by molecular beam epitaxy with an atomic‐plane sheet‐doping technique.

ISSN:0003-6951    

DOI:10.1063/1.97710

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Photoconductivity and Hall measurements in InP are presented for pressures up to 4 GPa using a diamond anvil cell. The application of pressure increases the direct energy band gap (E0), as seen by the shift of the photoconductivity edge to lower wavelength with increasing pressure. Hall measurements show a decrease in the electron mobility (&mgr;e) with pressure, due mainly to an increasing effective mass (m@B|e). Analysis of the pressure dependence of &mgr;eshows that polar optical scattering is the dominant mechanism.

ISSN:0003-6951    

DOI:10.1063/1.97711

出版商:AIP    

年代:1987

数据来源: AIP