摘要:

Numerical techniques are developed to study the output spectra and to solve the coupled mode rate equations for InxGa1−xAs/Al0.3Ga0.7As quantum well lasers. The optical properties of the laser are calculated from a 4×4k⋅pband structure which includes the effects of strain. We find that the side modes are severely suppressed in the strained laser. Large signal switching of the laser is also studied and the role of strain is identified in the device response. If the laser is switched from the off state to a state of given photon density in thelasingmode, then the strained system exhibits a faster time response. If, however, the laser is switched from the off state to a state of giventotalphotondensity, then the strained system has a slower time response.

ISSN:0003-6951    

DOI:10.1063/1.106022

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A theory is presented for the propagation of elastic waves in a plate excited by scanning a laser beam at a constant velocity. A formula for the excitation by scanning a line‐focused laser beam is deduced from a general formula and analyzed extensively in a two‐dimensional model. It is derived that such modes of Lamb waves are selectively excited whose phase velocities match the scanning velocity. It is also shown that major characteristics of experimental observations previously made are explained with the present model.

ISSN:0003-6951    

DOI:10.1063/1.106023

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on the growth of high‐quality diamond using a microwave plasma chemical vapor deposition (CVD) system in which the feed gas contains no hydrocarbons, but instead the source of carbon is a graphite piece which resides within the plasma volume. Results of experiments using this technique by itself and in combination with the normal methane feed gas method are described. The samples were analyzed by Raman spectroscopy and scanning electron microscopy. Diamond grown in this way was found to be particularly pure and of high crystallinity.

ISSN:0003-6951    

DOI:10.1063/1.106024

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Ferroelectric thin films of Bi4Ti3O12were fabricated on several types of substrates, including quartz, steel plates, and indium‐tin‐oxide coated glass slides, by sol‐gel technique. Crystalline, transparent, and crack‐free films of 5000 A˚ thickness were fabricated by spinning and post‐deposition annealing at a temperature of 550 °C. Ferroelectric properties were confirmed byP‐Ehysteresis loops. The dielectric constant and optical transmission were also measured.

ISSN:0003-6951    

DOI:10.1063/1.106025

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Model calculations are described which predict the fraction of tetrahedral (sp3) versus graphitic (sp2) bonding in ion beam or plasma‐deposited amorphous carbon films on the basis of the preferential displacement ofsp2atoms. Displacement yields obtained from statictrimsimulations are used as input data for a simple analytical growing layer model of ion beam deposition. Thesp3/sp2ratio is found to increase with increasing carbon ion energy between 30 eV and 1 keV. Assuming equal probabilities for a free (implanted or displaced) atom to become trapped at eithersp2orsp3sites results insp3/sp2ratios between 1 and 3.5. More refined dynamic simulations withtridynconfirm the trends with slightly lowersp3/sp2ratios for ion beam or plasma deposition, also involving hydrogen. A decrease of thesp3/sp2ratio towards high energies cannot be explained by preferential displacement only, in contrast to proposals in recent literature.

ISSN:0003-6951    

DOI:10.1063/1.106026

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

State‐of‐the‐art quality Al0.3Ga0.7As was achieved on both (111)B and (100) GaAs by molecular beam epitaxy. Low‐temperature photoluminescence linewidths of 2.9 and 2.4 meV were obtained for (111)B and (100) Al0.3Ga0.7As, grown at 650 and 700 °C, respectively, with nearly equivalent integrated luminescence intensity. This is the narrowest linewidth ever reported for (111) AlGaAs. The low growth temperature and high material quality of (111)B Al0.3Ga0.7As is expected to be an important factor to the future development of both electronic and optical heterostructure devices.

ISSN:0003-6951    

DOI:10.1063/1.106409

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The window for the ALE self limited growth of GaAs can be expanded by reducing the gas phase decomposition. We found that the exposure time to TMGa flux is critical and has to be reduced for ALE to be achieved at high growth temperature. An ALE reactor was used which allows minimum gas heating, short exposure time, and sudden termination of the gas exposure without relying on the diffusion of gases away from the substrate surface. ALE was achieved in the 450–700 °C temperature range. Carbon doping in the 1015–1020/cm3range was also achieved by adjusting the exposure time and the growth temperature. The combined role of gas phase decomposition and surface reaction are proposed to explain these results.

ISSN:0003-6951    

DOI:10.1063/1.106027

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have studied crystal defects of devices with oxide filled trench isolation introduced by high dose (∼1015cm−2) arsenic implantation at 40–80 keV and the dependence of their growth on oxidation conditions. Cross‐sectional views of the devices are observed by transmission electron microscopy. Solid phase epitaxial regrowth becomes very slow at the edge of the silicon island. Oxidation of the silicon substrate is influenced by the stress generated in the oxide filled trench structure. Defect density after oxidation (1) is higher for pyrogenic H2+O2oxidation than for dry oxidation, (2) is lower at the edge than in the central region of the silicon island, and (3) decreases significantly for a low energy arsenic implantation (40 keV).

ISSN:0003-6951    

DOI:10.1063/1.106028

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Al/GaAs Schottky barriers are fabricated with 2.5–20‐A˚ thick doping layers of Ce of concentrations 1020cm−3and 1021cm−3situated below the GaAs surface. Schottky barrier heights (SBHs) are determined from current‐ and capacitance‐voltage measurements.n‐type SBHs decrease with increasing Ce doping layer thickness, whilep‐type SBHs increase, but to a lesser degree. A cross‐sectional image taken by high‐resolution transmission electron microscopy shows that Ce is located in the substitutional sites of the doping layers. The changes in the SBHs are attributed to strain induced by Ce atoms in the substitutional sites. The difference in the magnitudes of change observed forn‐ andp‐type SBHs is discussed in relation to the inhomogeneity observed in the density of Ce atoms at the interface regions.<pc;normal>

ISSN:0003-6951    

DOI:10.1063/1.106029

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Raman light scattering experiments in lattice‐matched InGaAsP/InP multiple quantum wells are reported. Use of laser light below the InP band gap permitted study of right‐angle scattering with the scattered light emerging parallel to the layers. Scattering by the binary InP longitudinal optic (LO) and transverse optic (TO) phonons dominated the spectra. The polarization selection rules for the TO and LO scattering were found to differ strongly compared to those operative in bulk InP. This is interpreted as arising from the interchange of the LO and TO phonon frequencies as expected in a dielectric continuum slab whose thickness is small compared to the wavelength of the incident radiation. In addition weak Raman scattering by a mixture of InGaAs and InP vibrations in the quaternary well material is reported.

ISSN:0003-6951    

DOI:10.1063/1.106030

出版商:AIP    

年代:1991

数据来源: AIP