摘要:

The first room‐temperature two‐dimensional heavy hole exciton red shift, greater than 25 meV due to the exchange of Van Hove‐typeM1and quantum well excitons, was observed by photocurrent measurements in molecular beam epitaxy grown superlattices with periods of 30 A˚ GaAs/25 A˚ Ga0.5Al0.5As. At a photon energy of 1.66 eV, a 3000 cm−1absorption change due to the blue shift of the superlattice absorption edge was also observed at room temperature in superlattices with periods of 20 A˚ GaAs/20 A˚ Ga0.5Al0.5As.

ISSN:0003-6951    

DOI:10.1063/1.101326

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have investigated the lateral width (Lx) dependence of the quantum efficiency of the excitonic recombination in etched InGaAs/InP wires (40 nm≤Lx≤5 &mgr;m). The analysis of data obtained at different temperatures implies that the intensity decay observed for narrow wires is due to the formation of an optically inactive (‘‘dead’’) layer and due to surface recombination.

ISSN:0003-6951    

DOI:10.1063/1.101327

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The morphology and microchemistry of interfaces in GaInAs/InP quantum well structures have been studied with extremely high resolution by the new technique of position sensitive atom probe microanalysis. This letter presents some preliminary results demonstrating the power of the technique in determining the structure and chemistry of individual interfaces in multilayer epitaxial semiconductor samples.

ISSN:0003-6951    

DOI:10.1063/1.101328

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The excess carrier lifetimes in a silicon doping superlattice were investigated by measuring the decay of both the photovoltage and the photoconductance. The photovoltage decayed exponentially with a time constant of 1 s at liquid‐nitrogen temperature. In addition, persistent photoconductivity extending over many hours was observed in then‐type layers.

ISSN:0003-6951    

DOI:10.1063/1.101312

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Hydrogen passivation of the clean Si(100) surface to prevent growth of native oxides after air exposure was studied by supplying atomic hydrogen at several temperatures between room temperature and 650 °C. Atomic hydrogen was generated with high efficiency by the electron cyclotron resonance plasma cell of the gas source Si molecular beam epitaxy apparatus. The passivation effect was examined by observing the oxygenKLLAuger peak height of the passivated wafer after 12 h air exposure. The wafer supplied with atomic hydrogen at temperatures below 400 °C showed an obvious passivation effect, while the wafer supplied with hydrogen at temperatures above 400 °C showed no passivation effects. The solid source Si MBE growth was done on these hydrogen‐passivated and 12 h air‐exposed wafers at the growth temperature of 600 °C without any initial surface cleaning process. A good crystal quality film which showed a sharp 2×1 reflection high‐energy electron diffraction pattern was obtained on the wafer supplied with hydrogen at temperature below 400 °C.

ISSN:0003-6951    

DOI:10.1063/1.101313

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The hole transport through the minibands of a GexSi1−x/Si superlattice is observed for the first time. The symmetrically strained, short‐period GexSi1−x/Si supperlattice is grown on a Gex/2Si1−x/2/Si buffer layer. The current‐voltage and conductance‐voltage characteristics show two peaks which are attributed to the conduction of light holes through the first and second light hole minibands. The light hole miniband energies are estimated by thermionic emission analysis and are in good agreement with the calculated values using effective mass approximation.

ISSN:0003-6951    

DOI:10.1063/1.101314

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Exposure of plasma deposited silicon nitride to 193 nm ArF excimer laser radiation suppresses the etch rate in buffered HF solution by as much as a factor of 50. Using a contact mask, 0.23 &mgr;m lines and spaces were transferred into silicon nitride by this exposure and etching technique. The mechanism involves transient thermal annealing induced by the 15 ns laser pulses, which reduces the concentration of NH and SiH groups.

ISSN:0003-6951    

DOI:10.1063/1.101315

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have studied P ion implantation induced intermixing of In0.53Ga0.47As quantum wells embedded between InP barriers. Data are presented for both standard furnace anneals at 650 °C and rapid thermal anneals at 750 °C. Low‐temperature photoluminescence and quantitative Auger electron spectroscopy were performed for furnace‐annealed samples for which photoluminescence shifts of ∼200 meV were in excellent agreement with the calculated band gap for the lattice matched composition determined by Auger spectroscopy. Photoluminescence studies of rapid thermal annealed samples yield an energy gap shift of ∼150 meV for annealing times of at least 10 s.

ISSN:0003-6951    

DOI:10.1063/1.101316

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Thin films of YBaCu(F)O were deposited on SrTiO3(100) substrates by multilayer deposition from three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5Torr of O2. The films were later annealed in a separate chamber under a flowing O2‐H2O atmosphere. X‐ray diffraction studies reveal that the resulting structure is highly oriented with theaaxis perpendicular to the substrate. Scanning electron micrographs show a morphology consisting of an array of orthogonal, interconnecting bars with well‐developed junctions. High‐resolution electron microscopy and electron diffraction patterns show that these junctions are atomically abrupt and that the associatedcaxes are mutually perpendicular. These epitaxial films show a sharp resistive transition withTc(R=0) as high as 90 K. The zero field critical current density, determined from magnetization measurements, is 2.9×106A/cm2at 4.2 K and 5.0×104A/cm2at 77 K.

ISSN:0003-6951    

DOI:10.1063/1.101317

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have prepared 90% single‐phase bulk samples of the 110 K superconducting phase of the Bi‐Sr‐Ca‐Cu‐O compounds with different Pb amounts. Critical superconducting temperatures (zero resistance) of up to 109 K were measured in the bulk samples. X‐ray powder diffraction patterns of the almost isolated 110 K phase are presented. Computer‐simulated diffractograms were obtained, which are in general agreement with the measured ones. A discussion of the role of Pb in the stability of the 110 K phase in this compound is presented.

ISSN:0003-6951    

DOI:10.1063/1.101318

出版商:AIP    

年代:1989

数据来源: AIP