摘要:

SiO2films containing Si nanocrystals (nc-Si) and Er were prepared and their photoluminescence (PL) properties were studied. The samples exhibited luminescence peaks at 0.81 and 1.54 &mgr;m, which could be assigned to the electron-hole recombination in nc-Si and the intra-4ftransition inEr3+,respectively. Correlation between the intensities of the two luminescence peaks was studied as functions of Er concentration and excitation power. The present results clearly demonstrate that excitation ofEr3+occurs through the recombination of photogenerated carriers spatially confined in nc-Si and the subsequent energy transfer toEr3+. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119624

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ge islands were deposited on Si(001) partially covered with patterned oxide. Selective Si was deposited on some wafers before Ge deposition to form raised Si(001) plateaus with well-defined sidewall facets. On narrow lines, the Ge islands locate preferentially at the edges of the raised Si(001) regions, and the preference is strongest on the narrowest patterns aligned along a ⟨100⟩ direction. For a 450 nm wide plateau aligned in this direction, all the islands are positioned along the edges of the pattern, with a 300 nm space near the center of the pattern free of Ge islands. The islands appear to be uniformly spaced along the pattern edges. On wider lines, several rows of islands are aligned near the edges of the pattern, with the order decreasing farther from the edge. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119625

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Epitaxial lateral mask overgrowth which occurs during GaN selective epitaxy has been studied using linear mask features. The lateral growth varies between its maximum and minimum over a 30° angular span and exhibits hexagonal symmetry. Vertical growth follows an opposite trend, with lateral growth maxima, and vertical growth minima occurring for lines parallel to the GaN ⟨10•0⟩. Large variations in the lateral growth are also obtained through variations in the growth temperature andNH3flow. Under proper growth conditions, lateral to vertical growth rate ratios of up to 4.1 can be achieved, resulting in significant lateral mask overgrowth and coalescence of features without excessive growth times. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119626

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have studied stable structures of hydrogenated Si clusters grown from silane gas in an ion trap developed for cluster growth. The grown clusters were extracted from the ion trap through two different pathways and were analyzed by mass spectrometers. TheSi6Hx+cations were stably grown, among them clusters withx=1,7, and 13 were always observed, regardless of the growth conditions or the extraction pathways. The stable structures of these clusters were theoretically investigated. Clusters ofx=1,7, and 13 corresponded to the compact structure, the intermediate structure which has both compact and bulklike configurations, and the bulklikesp3structure, respectively. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120452

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Minority-carrier response and conductance loss characteristics ofSiNx/Si/Ge/n-GaAs(001)metal–insulator–semiconductor (MIS) structures are presented. The response time of minority carriers withSi(⩽10 Å)/Ge(20 Å) interlayers, as determined by the capacitance–voltage(C–V)method, is several orders of magnitude smaller than those with Si interlayers only. The minority carriers inn-type Si/Ge/GaAs layers respond to even a small ac signal of 1 kHz at room temperature, which is ascribed to the smaller band gap and thus a higher intrinsic carrier concentration of Ge. The minority carriers in theSiNx/Si/Ge/n-GaAsMIS structures respond to a 1 MHz signal at a sample temperature of 230 °C. Temperature-dependentC–Vmeasurements on the GaAs MIS structure with Si/Ge, interlayers revealed the activation energy(Ea)of the minority-carrier recombination to be about 0.58 eV. The conductance loss characteristics ofSiNx/Si/Ge/GaAsstructures indicate a contribution by interface traps responding to slow states, while the fast states are a result of interface defects of theSiNx/Si/GaAsMIS system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119853

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the observation of zero-dimensional (0D) excitonic confinement in locally strainedZn1−xCdxSequantum wells. Strain fields from self-organized CdSe quantum dots are used to locally modulate the band structure of a nearby quantum well in a heterostructure, resulting in confinement in all three dimensions. The 0D nature of excitonic confinement is verified by the observation of sharp lines in photoluminescence (PL) spectra. The temperature dependence of the PL lifetime is markedly different than that of the CdSe quantum dots. High-resolution spectra show that the PL lines from the localized states are split into linearly polarized doublets. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119854

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Modifications of noise performances induced by hot-carrier degradation in polycrystalline silicon thin-film transistors, made by excimer laser crystallization, are presented. In particular, the normalized drain current spectral density of these devices shows an evident1/fbehavior, and as the device characteristics are degraded by prolonged bias stressing, the noise performances worsen. Hot-carrier degradation results in the formation of both interface states, that have been evaluated through the analysis of the sheet conductance, as well as of oxide traps near the insulator/semiconductor interface, as evidenced by the1/fnoise measurements. A strong correlation between interface state and oxide trap densities has been found, suggesting a common origin for the generation mechanism of the two types of defects. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119855

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A bistable GaAs–InGaP triangular-barrier optoelectronic switch (TBOS), grown by metalorganic chemical vapor deposition, was fabricated. By introducing avalanche multiplication and carrier confinement into the device operation, S-shaped negative-differential-resistance performances are observed in the current–voltage(I–V)characteristics under normal and reverse operation modes. The TBOS shows a flexible optical function related to the potential barrier height controllable by incident light. The dependence of the carrier transport mechanism on the illumination was investigated. TheI–Vcharacteristics at different temperatures were also discussed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119856

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The effects of lost phase coherence on carrier capture by semiconductor quantum wells are simulated using Schro¨dinger Equation Monte Carlo. Results are shown for polar-opticalphonon-induced capture of both electrons and holes, and for both monoenergetic and thermal distributions of incident charge carriers. Results suggest that semiclassical modeling of hole capture may be sufficient, provided that quantum mechanical reflection from the individual heterointerfaces still is taken into account. However, for a quantum well laser optimized to operate at an electron capture resonance, semiclassical calculations blind to the resonance structure would underestimate the capture rate, whileGolden-Rulecalculations, which assume complete phase coherence, could somewhat overestimate it. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119857

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Using weak beam dark-field transmission electron microscopy, we have identified, by reference to stacking fault trapezoids, an additional crystal defect, a stacking fault tetrahedron, at the interface of ZnSe/GaAs(001) epilayers. Unlike the other stacking faults which are basically of uniform size, the size of stacking fault tetrahedra can vary by a few times, with a typical value of less than 10 nm. The stacking fault tetrahedron is a closed defect and does not extend very far from the interface. The density of the stacking fault tetrahedra is at least as high as that of the dominant stacking faults trapezoids. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.119858

出版商:AIP    

年代:1997

数据来源: AIP