摘要:

Ga2O3(Gd2O3)was deposited on GaN for use as a gate dielectric in order to fabricate a depletion metal–oxide–semiconductor field-effect transistor (MOSFET). Analysis of the effect of temperature on the device shows that gate leakage is significantly reduced at elevated temperature relative to a conventional metal–semiconductor field-effect transistor fabricated on the same GaN layer. MOSFET device operation in fact improved upon heating to 400&hthinsp;°C. Modeling of the effect of temperature on contact resistance suggests that the improvement is due to a reduction in the parasitic resistances present in the device. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122927

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In order to determine dissociation energy of the 1.014 eV photoluminescence (PL) Cu center in silicon crystal, decay of the PL intensity of the center by annealing samples at various temperatures was measured. The samples were prepared by contamination of Cu from Cu solution and heat treatment at 700 °C followed by rapid cooling to room temperature. From the temperature dependence of the time constant of the decay of the PL center, activation energy of dissociation of the center was obtained. The value was 0.47+±0.05 eV, which was much smaller than that (1.02 eV) obtained by the decay of the deep level transient spectroscopy Cu center peak atEv+0.09eV. The present value could reasonably explain the rapid thermalization of rearrangement of the centers after the release of stress which had been observed earlier. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122928

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Oval defects inIn0.04Ga0.96As/GaAsstrained-layer heterostructures have been investigated using cathodoluminescence (CL) and wavelength dispersive x-ray spectroscopy (WDS). WDS studies showed that the particulates seen at the center of oval defects are indium rich and gallium depleted. A luminescent halo was seen around the indium rich particulates in the CL mode. When the halo was studied further, it was shown that the peak obtained from CL spectroscopy due to the luminescent halo shifts to lower wavelengths as the beam is moved from the center of the oval defect to the edge of the halo region, indicating a decreasing gradient in indium concentration. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122929

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Si nanowires with uniform size have been synthesized by laser ablation of highly pure Si powder targets mixed withSiO2.A bulk quantity of Si nanowires was successfully obtained by mixing 30&percent;–70&percent; ofSiO2into the Si powder target.SiO2played a crucial role in enhancing the formation and growth of the Si nanowires. The morphology and microstructure of the Si nanowire tips have been systematically characterized by means of high-resolution transmission electron microscopy. No evidence of metal was found at the tips. The results suggest that Si oxide is more important than metal in catalyzing the formation of Si nanowires. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122930

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

CuPt ordering results in a reduction of the band-gap energy of GaInP. Thus, heterostructures and quantum wells can be produced by simply varying the order parameter, without changing the solid composition. Changes in the order parameter can be induced by changes in growth conditions. The disordered/ordered/disordered quantum wells described here are grown by changing thePH3flow rate. Transmission electron microscopy results show that the quantum wells produced in this way are clearly defined, with abrupt interfaces. Low-temperature photoluminescence spectra show distinct peaks from quantum wells (QWs) of different widths. The QW photoluminescence peak energy increases with decreasing well width due to quantum size effects. The difference in band-gap energy between the ordered and disordered single layers is determined from photoluminescence excitation spectroscopy to be 0.06 eV. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122931

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Thermally induced strain caused by device packaging is studied in high-power semiconductor lasers by a noninvasive technique. Fourier-transform photocurrent measurements with intentionally strained laser array devices for 808 nm emission reveal spectral shifts of quantum-confined optical transitions in the optical active region. These shifts by up to 7 meV serve as a measure for strain and are compared with model calculations. For a given packaging architecture, about one quarter of the mounting-induced strain is transferred to the quantum-well region of the device. Spatially resolved measurements demonstrate a lateral strain gradient in the devices. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122932

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We study the temperature dependence of the current–voltage and radiance–voltage curves in double-carrier injected polymer light-emitting devices comprised ofpoly(2-methoxy,5-(2′-ethyl-hexoxy)–p-phenylene&hthinsp;vinylene)(MEH–PPV) andMEH–PPV/SiO2as the active layer. The quantum efficiency increases significantly as the temperature is decreased in agreement with an increase in the recombination efficiency with decreasing temperature. Moreover, the bimolecular recombination efficiency saturates at low temperatures and high currents to a very high value for both the composite and plain MEH–PPV devices with the nanoparticles serving as charge traps only at moderately low current densities. Finally, we find that the order of magnitude improvement in radiance observed in some polymer/nanoparticle composites is due to an increase in the effective electric field across the device. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122933

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The current–voltage characteristics of light-emitting devices containing thin films of poly(dialkoxy-p-phenylene vinylene) (PPV) incorporated with silicon dioxide nanoparticles have been investigated. It is demonstrated that the current enhancement of the devices containing composite layers can be modeled by assuming that the effective thickness of the composite layers is about half of their actual thickness. Field-effect measurements reveal that the mobility of the charge carriers in PPV is not significantly changed by the incorporation of nanoparticles. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122934

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The internal photoemission method was used to measure the Schottky barrier height of Ni on AlGaN/GaN heterostructures. A barrier height of 1.31 eV was found for theNi/Al0.15Ga0.85N/GaNheterojunction structure, as compared to a barrier height of 1.28 and 1.02 eV for theNi/Al0.15Ga0.85Nand Ni/GaN Schottky diodes, respectively. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122935

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The variation of barrier height with the band gap in the metal/heterojunction systems is related to how the Fermi level position varies with respect to band edges. If the Fermi level is pinned by the interface states its movement will also correspond to the movement of the neutrality level at the interface. Metal/Si1−xGex/Siheterostructures(0⩽x⩽0.24)for bothn- andp-type substrates were studied to understand the relation between Schottky barrier, Fermi level movement, and the band gap variations. It was shown that a correlation exists between Schottky barrier height variation and band-offset values&Dgr;Ecand&Dgr;Ev.Forn-type substrate, measured barrier height differences are almost the same as the band offsets in the conduction band&Dgr;Ec.Forp-type substrates they were found to be slightly smaller than&Dgr;Ev.This shows that Fermi level position relative to the conduction band edge does not change with band gap variation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122936

出版商:AIP    

年代:1998

数据来源: AIP