摘要:

Defect annealing under intense pulsed optical excitation has been observed in a II–VI laser diode structure at room temperature. More than one order of magnitude increase in photoluminescence intensity has been obtained when the annealed area is probed at low excitation intensity. High-resolution confocal photoluminescence images of the annealed region do not show any sign of degradation. Together, these results suggest that an initial density of intrinsic point defects present within the active region can be removed by the optical annealing. Recombination-enhanced defect reactions in the vicinity of the point defects are responsible for this nonthermal annealing effect. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120682

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Growth by vapor phase epitaxy around stripe mesas and in trenches formed by reactive ion etch on 6H and 4H SiC substrates has been investigated. The mesas were aligned with the low index ⟨112¯0⟩ and ⟨11¯00⟩ directions, as well as with the high index⟨1,1+&sqrt3;,2+&sqrt3;,0⟩directions, in order to reveal and study the growth habit. It was found that a low C:Si ratio gave a smooth growth and small differences in growth rate between lattice planes. A larger C:Si ratio gave more faceted growth, both limited by surface kinetics and surface diffusion, and the growth rate was 10&percent; lower in the [11¯00] direction and 10&percent; higher in the [112¯0] direction, than on the substrate. Growth on mesas oriented parallel to the substrate off-orientation shows clear step-flow growth, while growth on mesas oriented perpendicular to the off-orientation reveals the singular (0001) plane, where islands are observed, which might indicate Stranski–Krastanov growth. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120683

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Carbon diffusion into silicon is well behaved and does not generate any nonequilibrium point defects. We show that, in contrast, the diffusion of carbon incorporated in silicon well above its solid solubility will cause an undersaturation of silicon self-interstitials, which in turn may cause retarded diffusion of boron. In addition, we predict that due to this undersaturation, the diffusion of built-in carbon spikes will lead to strongly non-Gaussian concentration profiles. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120684

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have fabricated and characterized a low-noise direct-coupled magnetometer based on a 100 pHYBa2Cu3O7−xdc superconducting quantum interference device (SQUID) on a 10 mm×10 mm SrTiO3bicrystal substrate with 30° misorientation angle. The thin films were deposited by hollow cathode discharge sputtering and patterned using conventional photolithography and Ar ion beam etching. The SQUID magnetometer was operated using direct-coupled flux-locked-loop electronics with bias reversal. The sensor had a usable voltage swing of 39 &mgr;V and a white magnetic field noise of 32fTHz−1/2with a 1/fcorner at 2 Hz, including electronics and environmental noise. The voltage versus flux(V−&Fgr;)characteristic showed a pronounced distortion on the negative slope. Numerical simulations were performed to explain the distortedV−&Fgr;characteristic. Measurements of magnetocardiograms demonstrate the suitability of this sensor for biomagnetic applications. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120685

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

By studying the diffusion of specially incorporated thin Mn markers in molecular beam epitaxy-grown CdTe, we can investigate quantitatively deviations from stoichiometry as well as the details of Cd diffusion in the crystal. In CdTe layers deficient in Cd, the diffusion proceeds throughVCdvacancies, with the activation energy of 2.1 eV, characteristic for bulk CdTe. In CdTe grown in excess Cd flux, the evaluated activation energy of 1.4 eV for Cd self-diffusion is characteristic to Te self-diffusion in bulk CdTe, which implies that the flow of Cd atoms is mediated byVTevacancies with formation of a virtualCdTeantisite defect. A striking correlation of the occurrence of the minimum of electrical resistivity in In-doped CdTe with nearly perfect stoichiometry with the minimum of the diffusivity of Mn provides further support of this interpretation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120686

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In this letter, we introduce a new thin film solar cell design on amorphous silicon, called the transverse junction solar cell. In this concept, thep-i-njunction is formed perpendicular to the surface. With conventional deposition and silicon device processing techniques test cells have been made with a conversion efficiency up to5.2&percent;±1.4&percent;under standard AM1.5 illumination. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120687

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

InGaN multi-quantum-well-structure laser diodes withAl0.14Ga0.86N/GaNmodulation doped strained-layer superlattice cladding layers grown on an epitaxially laterally overgrown GaN (ELOG) substrate was demonstrated to have a lifetime of more than 1150 h under room-temperature continuous-wave operation. After 4 &mgr;m etching of the ELOG substrate, the etch pit density was about2×108cm2in the region of the 4-&mgr;m-wide stripe window, but almost zero in the region of the 7-&mgr;m-wideSiO2stripe. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120688

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Data are presented on the electroluminescence from an ensemble of self-organized quantum dots excited at low current densities. The ensemble contains∼105dots, which produce a ground state spectral emission with a 14 K linewidth of ∼1 meV at low current density(∼5×10−2A/cm2).While the spectra show clearly discrete energy levels, we suggest that obtaining a single ground state emission from the ensemble may be due to interdot electronic coupling. Spectral broadening decreases for decreasing current density due to electronic state filling, even for the lowest current densities studied. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120689

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We study through high-resolution x-ray diffraction (HRXRD) and photoluminescence spectroscopy a series ofZn1−xCdxSe/ZnSemulti-quantum-well heterostructures grown by molecular-beam epitaxy on relaxed ZnSe buffer layers, themselves grown on bare GaAs substrates. We show that HRXRD experiments combined with simulations allow one to accurately assess the strain state of the heterostructures which appear to follow closely the Matthews and Blakeslee model [J. Cryst. Growth27, 118 (1974)]. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120690

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The lattice-mismatch stress-induced two-dimensional-to-three-dimensional morphology change is combined with interfacet adatom migration to selectively assemble parallel chains of InAs islands on top of [11¯0] oriented stripe mesas of sub-100-nm widths on GaAs(001) substrates. On such mesa stripes, preparedin situvia size-reducing epitaxy, deposition of InAs amounts subcritical for island formation on planar GaAs (001) is shown to allow self-assembly of three, two, and single chains of InAs three-dimensional island quantum dots selectively on the stripe mesa tops for widths decreasing from 100 nm down to 30 nm. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120691

出版商:AIP    

年代:1998

数据来源: AIP