摘要:

Diffusion of Si adsorbates deposited on a Si(001) surface is investigated by reflection electron microscopy. At temperatures up to about 600 °C, the diffused lengthxof the adsorbates is proportional tot1/4before the critical timetc,wheretis the heating time. Att<tc,xis determined by a length at which atoms collide with others on the surface. Att>tc,the diffused lengthxis proportional tot1/2,wherexis determined by thermal diffusion of the adsorbates. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119765

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The polarization of photoluminescence (PL) was investigated on (11¯00) GaN grown by metalorganic vapor phase epitaxy. We found that the PL intensity and wavelength have polarization dependence parallel and perpendicular to thecaxis. We quantitatively analyzed the dependence and found that, since the crystal field of wurtzite GaN along thecaxis is strong enough to fix the|z⟩axis ofpfunctions at thecaxis, the difference in symmetry between three valence bands appears as the polarization anisotropy in radiative emission, even in bulk GaN. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119766

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The velocity-field characteristics in zinc-blende GaN are calculated from the Boltzmann equation, using realistic energy bands taken fromab initiotheory. The drift velocity and the high-field negative differential resistance are shown to be largely determined by the inflection point in the bands centered around the &Ggr; valley, instead of the usual intervalley scattering. We analyze the relative importance of these competing mechanisms for GaN andAl0.5Ga0.5N.The importance of this anomaly to device properties is also discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119767

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The fabrication and enhanced performance of a polycrystalline silicon high voltage thin film transistor structure, which incorporates a semi-insulating field plate, are reported. For comparison, the performance of conventional offset drain and metal field plate structures, fabricated on the same wafer using the same low temperature(⩽610 °C)polycrystalline silicon process, is described. Electrical characterization of the high voltage thin film transistor structures demonstrates that the new three terminal device offers the highest blocking capability(>200 V)without sacrificing on state performance. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119768

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Extremely uniform and high-densityGaAs/(GaAs)4(AlAs)2quantum wires (QWRs) were self-organized in a thinGaAs/(GaAs)4(AlAs)2quantum well grown on a (775)B GaAs substrate with a regularly corrugated AlAs–on–GaAs interface and a flat GaAs–on–AlAs interface by molecular beam epitaxy. A strong photoluminescence (PL) peak at &lgr;=692 nm from the GaAs/(GaAs)4(AlAs)2QWRs showed large polarization anisotropy[P=(I∥−I⊥)/(I∥+I⊥)=0.19]. A full width at half-maximum of the PL peak from the QWRs was as small as 15 meV at 14 K, which is smaller than those of any self-organized GaAs/AlGaAs QWRs reported so far. Density of the QWRs (8×105QWRs/cm) is the same as the highest ever reported. These results indicate that the QWRs grown on the (775)B GaAs substrate meet requirements for applications to QWR lasers (high uniformity, high density, high optical quality, and simple fabrication process). ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119769

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A scanning tunneling microscope was used to generate electroluminescence (EL) from thin films of the conjugated polymer poly(1,3-phenylenevinylene-co-2,5-dioctyloxy-1,4-phenylenevinylene). This allowed the spatial distribution of EL to be mapped across the film, and also measurements of local EL emission spectra to be recorded. It was observed that both the emission spectra and their intensity are highly nonuniform on length scales≳2 nm.This is important in the context of light emitting diodes since it indicates that control of nanostructure can greatly improve device performance. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119770

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the intensity dependence of the responsivity in quantum well infrared photodetectors (QWIP). A strong reduction of the responsivity is observed already at small excitation powers for a QWIP withN=4periods. This nonlinearity is caused by a partial screening of the electric field across the main part of the active region. The intensity dependence is analyzed using a phenomenological approach, which allows us to calculate the nonlinearity from the measured dark current and responsivity. Applying this approach to a background-limited 50 period QWIP, we find that the nonlinearity is already present below1 mW cm−2,which is less than the thermal background. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119771

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The initial stages of GaAs overgrowth over self-assembled coherently strained InAs quantum dots (QDs) are studied. For small GaAs coverages (below 5 nm), atomic force microscopy (AFM) images show partially covered island structures with a regular size distribution which are elongated in the [011] direction. Analysis of the AFM profiles show that a large anisotropic redistribution of the island material is taking place during the initial GaAs overgrowth. Short time annealing experiments together with photoluminescence spectroscopy on annealed QDs are consistent with a Ga and In intermixing during the overgrowth. Surface QDs capped with 5 nm or more GaAs show a strong luminescence intensity indicating that surface QDs are remarkably insensitive to surface recombination effects. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119772

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A dual-band multiple quantum well infrared photodetector has been fabricated for the near and mid-infrared detection. The structure consists of InGaAs/GaAs step quantum wells separated by AlGaAs/GaAs superlattice barriers. The step quantum wells are designed to have two bound states and a quasi-continuum above the superlattice barriers. The bound-to-bound and bound-to-continuum transitions are employed for the dual-band detection. The superlattice barriers are used to extract the photocurrent from the bound-to-bound transition with a relatively low external electric field, which keeps the dark current low. This work demonstrates the use of a new quantum well structure for the fabrication of multicolor quantum well infrared photodetectors. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119773

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This letter describes the fabrication of functional GaAs/AlGaAs field effect transistors using micromolding in capillaries—a representative soft lithographic technique. The fabrication process involved three soft lithographic steps and two registration steps. Room temperature characteristics of these transistors resemble those of field effect transistors fabricated by photolithography. The fabrication of functional microelectronic devices using multilayer soft lithography establishes the compatibility of these techniques with the processing methods used in device fabrication, and opens the door for their development as a technique in this area. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119774

出版商:AIP    

年代:1997

数据来源: AIP