摘要:

Experimental data of energy gaps, band offsets, and energy levels in AlxGa1−xAs/GaAs quantum wells are utilized for the determination of &Ggr; electron and light hole effective masses in AlxGa1−xAs compounds on the basis of the author’s relations between these quantities. The temperature dependences of electron and light hole effective masses in GaAs are also obtained.

ISSN:0003-6951    

DOI:10.1063/1.102898

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

By using a graded composition InAsSbP quaternary layer grown by liquid phase epitaxy it was possible to fabricate light‐emitting diodes which emit near 4.2 &mgr;m at room temperature, corresponding to the fundamental absorption of CO2gas.

ISSN:0003-6951    

DOI:10.1063/1.102899

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Epitaxial (111)CdxPb1−xTe//(111)BaF2films in the rocksalt structure have been made by codeposition from CdTe and PbTe magnetron targets in an rf discharge onto chemipolished substrates at 320 °C. Films were prepared withxvalues from 0 to 0.47, well past the range of bulk thermodynamic solubility. Raman spectroscopy, Auger spectroscopy, and transmission electron microscopy showed phase segregation had not occurred. The lattice spacing in the growth direction was observed to be insensitive tox.

ISSN:0003-6951    

DOI:10.1063/1.102900

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A refractive electrostatic prism is used to switch a beam of ballistic electrons between different collectors in the two‐dimensional electron gas of an AlGaAs‐GaAs heterostructure. This represents a new concept in electronic switching which utilizes the electrostatically controlled refraction of ballistic electrons in high‐mobility two‐dimensional systems.

ISSN:0003-6951    

DOI:10.1063/1.102901

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Data are presented on the long‐term (≳8 yr) degradation of AlxGa1−xAs‐AlAs ‐GaAs quantum well heterostructure material because of the instability of underlying (internal) AlAs layers. Material containing thicker (>0.4 &mgr;m) AlAs ‘‘buried’’ layers (confining layers) is found to be much less stable than material containing thinner (≲200 A˚) AlAs layers. Hydrolysis of the AlAs layers because of cleaved edges and pinholes in the cap layers leads to the deterioration.

ISSN:0003-6951    

DOI:10.1063/1.102902

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

ReSi2thin films were grown on (001) silicon wafers by vacuum evaporation of rhenium onto hot substrates in ultrahigh vacuum. The preferred epitaxial relationship was found to be ReSi2(100)/Si(001) with ReSi2[010]∥Si⟨110⟩. The lattice matching consists of a common unit mesh of 120 A˚2area, and a mismatch of 1.8%. Transmission electron microscopy revealed the existence of rotation twins corresponding to two distinct but equivalent azimuthal orientations of the common unit mesh. Although the lateral dimension of the twins is on the order of 100 A˚, MeV He+backscattering spectrometry revealed a minimum channeling yield of 2% for a ∼1500‐A˚‐thick film grown at 650 °C. There is a very high degree of alignment between the ReSi2(100) and the Si(001) planes.

ISSN:0003-6951    

DOI:10.1063/1.103251

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A reduction of the GaAs surface recombination velocity due to a heavily carbon‐doped GaAs overlayer is reported. Metalorganic molecular beam epitaxy using trimethylgallium, triethylgallium, and elemental arsenic sources has been used to grow an epitaxial structure consisting of 1000 nm ofp=1×1017cm−3capped with 10 nm ofp=1×1020cm−3GaAs. Time‐resolved photoluminescence (PL) and PL excitation spectroscopy showed thisp+/pstructure to have a 3.2 ns carrier lifetime and strong band‐edge PL emission, whose intensity was nearly constant over an excitation photon energy range of 1.5–3.3 eV. The same wafer with thep+cap etched off exhibited a much shorter carrier lifetime and PL intensity that decreased exponentially with increasing photon energy, which is indicative of carrier losses to surface recombination. The specific contact resistivity of nonalloyed ohmic contacts to these heavily doped layers was observed to be in the mid 10−7&OHgr; cm2range, independent of measurement temperature from 77 to 340 K, suggesting a tunneling contact due to the narrow surface depletion layer.

ISSN:0003-6951    

DOI:10.1063/1.102903

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

It is shown that strain relaxation during annealing of Si/GexSi1−x/Si heterostructures is significantly enhanced if the strained GexSi1−xlayers are implanted withp(B) orn(As) type dopants below the amorphization dose. Comparison of strain relaxation duringinsituannealing studies in a transmission electron microscope between unimplanted and implanted structures reveals that the latter show residual strains substantialy below those for unimplanted structures. We propose that this enhanced relaxation is caused by increased dislocation nucleation probabilities due to the high point‐defect concentrations arising from implantation.

ISSN:0003-6951    

DOI:10.1063/1.102904

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The thickness dependence of the subgap optical absorption in plasma‐deposited hydrogenated amorphous silicon is carefully studied by photothermal deflection spectroscopy. The deep‐level defect concentration decays from the top surface into the bulk where it approaches the thermal equilibrium defect density. This defect profile is interpreted in terms of the annealing, during growth, of growth‐induced surface defects. It is also shown that this defect profile is compatible with the known growth‐temperature dependence of the defect density in amorphous silicon.

ISSN:0003-6951    

DOI:10.1063/1.102905

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Y‐Ba‐Cu‐O (YBCO) films were grown on (100)MgO and (100)Si substrates by the high‐pressure dc diode sputtering process. The target was a Y1Ba2Cu3Oxcompound, made by a solid‐state reaction. The sputtering gas was Ar‐50% O2and the total pressure was 1.5 Torr. As‐deposited superconducting YBCO films can be prepared at low substrate temperatures (420 °C) with a high discharge current. The phases of the as‐deposited films strongly relate to the discharge current and substrate temperature. The high concentration of active species (excited atoms and ions) in the plasma during deposition is the main factor that permits superconducting YBCO films to be formed at such low substrate temperatures.

ISSN:0003-6951    

DOI:10.1063/1.103252

出版商:AIP    

年代:1990

数据来源: AIP