摘要:

We show that with the introduction of a new pair of epitaxial layers, sandwiched between the active and cladding regions, self‐defocusing can play an important role in stabilizing the lateral mode in broad‐area semiconductor lasers and amplifiers. Under certain conditions, it can be used to eliminate filamentation and provide a nearly flat mode profile by adjusting the band gap of the new self‐defocusing layers. We discuss the use of a strained multiple‐quantum‐well laser for producing such a stable lateral mode. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117917

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have observed visible electroluminescence (EL) from silicon nanocrystallites which are embedded ina‐Si:H films prepared in a plasma enhanced chemical vapor deposition system. The EL spectra are in the range of 500–850 nm with two peaks located at about 630–680 and 730 nm, respectively. We found that the intensity of EL peaks is related closely to the conductivity of the deposited films. The carrier conduction path is discussed in terms of the material structural characteristics, and a tentative explanation of the light emission mechanism is proposed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117918

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Quantum efficiency in a polymer electroluminescence device is significantly improved by inserting a thin insulating layer with the thickness of tunneling range. Four times higher quantum efficiency was obtained without the increase of the threshold voltage. Poly(methyl methacrylate) Langmuir–Blodgett films were used as the thin tunneling barrier. The enhancement may result from the lowering of the effective barrier height for electron injection while increasing the effective barrier for hole injection. The effects improve the balanced injection of electrons and holes into the light‐emitting devices. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117919

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Early blue/green laser diodes based on ZnSe exhibited room temperature, continuous wave (cw) lifetimes of the order of a minute. Similar to the history of (Al,Ga)As lasers, the source of the degradation was the presence of extended crystalline defects. The dominant extended defects in the early room temperature cw lasers originated as stacking faults generated at the ZnSe/GaAs heterovalent nucleation event, and exhibited densities of the order of 106cm−2. In this letter, a procedure is described which will ensure a consistent run to run reduction of the density of such extended defects to the mid to low 103cm−2over a 3 in. wafer. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117920

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We propose a photodiode configuration suited for waveguide integration, and top and side illumination. This configuration based on a pair ofp‐i‐nphotodiodes, laid out alongside of one another, requires only one metallization type, and therefore, reduces the number of technological steps. A waveguide–photodiode integration illustrates this photodetector concept. The single heterostructure waveguide integrated evanescently with thisp‐i‐n‐i‐pphotodetector exhibits a 19 GHz bandwidth, as a result of the very low (30 fF) capacitance of a 20 &mgr;m long detector. Related to its symmetrical features, thisp‐i‐n‐i‐pphotodetector is a means to improve fabrication yield of integrated optoelectronic devices. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117921

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Light emitting devices with emission either in the blue, green, and red spectral region have been fabricated based on ladder‐type poly(p‐phenylene) (LPPP). Color tuning has been achieved simply by adjusting the LPPP layer thickness. Microcavity effects could be proven to control the shape of the electroluminescence and photoluminescence spectra of the single layer devices between aluminum and gold electrodes. The full width at half‐maximum was strongly reduced from ∼150 to 200 nm for the ‘‘free space’’ photoluminescence or for the electroluminescence spectra of devices with indium–tin oxide hole injecting electrodes to values between 60 and 70 nm for the three individual single color devices. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117922

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A theory is developed to explain the origin of physical phenomena in quasiwaveguide, based on the forward scattering and multiple‐wave interference effects. The properties of quasiwaveguide modes, such as positions, linewidths, the reflectivity of the reflected light spot, and the reflectivity distribution of scattered light are described. The shape of them‐lines is derived theoretically. Applications of the theory are also discussed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117923

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Two incident ultrasonic shear wave beams of 7.5 MHz interact at glass‐metal interface, and the reflected longitudinal wave of 15 MHz normal to the interface are investigated. This effect is identified as a nonlinear interface effect and the sum frequency signal is the convolution of two input signals. The convolution efficiency is measured as about 106 dBm for glass‐iron interface. The observation reveals that the quality of interface bonding has a significant influence on the convolution output. So the nonlinear effect is found to be useful for implementation of convolution or nondestructive evaluation of bonding layer. Theoretical analysis and experimental measurements on the effect are presented in this letter. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117924

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

High density oxygen plasmas (ne=1010–1013cm−3) are produced by a helicon wave discharge source with rf powers of 0.1–3 kW. Positive and negative ion species in the plasmas are measured by a time‐of‐flight mass spectrometer. The intensity ratio of O+to O+2increases with the electron densityneand is almost proportional to it in the region ofne=1010–1012cm−3. When the electron density increases up to 8×1012cm−3, the ratio becomes about 4. In a high density plasma of 1.3×1013cm−3obtained by mixing Ar gas, about 83% of the positive oxygen ions becomes O+. By using pulse modulation of the rf power, O−ions are mainly observed with remarkable increase in the afterglow. The maximum density of O−is about 3×1011cm−3at 30 &mgr;s after turning off the rf power of 0.85 kW and the decay time of O−is about 60 &mgr;s. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117925

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The effects of ArF excimer laser irradiation on silicon single crystals in air have been studied. The etch rate versus fluence curve shows three well defined zones, with very different etch rates and dependences. In the intermediate zone (from 1.5 to 2.5 J/cm2), narrow (1–2 &mgr;m diameter) and tall columns (3–30 &mgr;m) start to grow after irradiation with some hundreds of laser pulses. These whiskerlike columns, with height between one and two orders of magnitude higher than the depth of the crater, have not been formed by preferential etching of the surrounding material, but through hydrodynamical processes. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117926

出版商:AIP    

年代:1996

数据来源: AIP