摘要:

We report on the investigation of free-carrier absorption characteristics for epitaxially grownp-type silicon thin films in the far-infrared region (50–200 &mgr;m), where Si homojunction interfacial workfunction internal photoemission (HIWIP) detectors are employed. Five Si thin films were grown by molecular beam epitaxy on different silicon substrates over a range of carrier concentrations, and the experimental absorption data were compared with calculated results. The free-hole absorption is found to be almost independent of the measured wavelength. A linear regression relationship between the absorption coefficient and the carrier concentration, in agreement with theory, has been obtained and employed to calculate the photon absorption probability in HIWIP detectors. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119595

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A dual-material structure of lattice-matched GaInP on GaAs has a calculated figure of merit which is approximately 60 times better than Si and 5 times better than GaAs. In this work, the theoretical performance of the GaInP/GaAs structure is presented and experimental data for Ni on GaInP/GaAs Schottky rectifiers is presented. The Ni on GaInP/GaAs Schottky rectifiers have a breakdown voltage of ∼80 V and low reverse leakage current. Comparable Ni on GaAs Schottky rectifiers have a breakdown voltage of ∼20 V and significantly higher reverse leakage current. The GaInP/GaAs rectifiers’ forward characteristics have a current–voltage extracted&fgr;Bnof 1.0 eV with an ideality factor of 1.06. This dual-material structure of GaInP/GaAs appears to be a promising candidate for improving power device performance.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119596

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on optical experiments in self-assembled InAs quantum dots grown on (100) and (311)A GaAs surfaces which were precovered with Te. We observe a strong reduction of the luminescence intensity with increasing Te coverage in the (100)-oriented samples. The Te-induced luminescence reduction is, however, much smaller in the (311)A oriented samples. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119597

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optical-isothermal capacitance transient spectroscopy (O-ICTS) was used to characterize prominent midgap carrier traps in Si-dopedn-type GaN grown by metalorganic vapor phase epitaxy. Strong carrier photoionization was observed from two deep levels to the conduction band. The first level photoionizes in the broad range from below 1.8 eV to over 2.3 eV. Seen in alln-type GaN, this level is believed to be defect related and involved in the commonly observed yellow luminescence. The second, more dominant O-ICTS peak develops with incident photon energy of∼2.3 eV.This is a previously unreported, yet unidentified level of impurity nature. The two midgap states can be clearly distinguished by means of the time constant for photoionization of carriers from the deep levels. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119598

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The metalorganic vapor phase epitaxy of coherent self-assembled InAs islands on InP(001) is demonstrated. Samples are characterized using transmission electron microscopy and photoluminescence (PL) spectroscopy at 77 K. The deposition of ∼2.4–4.8 monolayers (ML) of InAs at 500°C followed by a 30 s growth interruption results in the formation of coherent islands whose average diameter is 30–35 nm with a standard deviation of 8 nm and whose areal density is(3–4)×1010cm−2.The PL emission is centered at 0.79 eV and has a full width at half maximum (FWHM) of 90 meV. When the nominal deposited thickness is increased to ∼9.6 ML, the average island diameter increases to ∼120 nm while the areal density decreases to∼109cm−2.The resulting PL is then centered at 0.83 eV with a FWHM of 130 meV and also displays a peak at 1.23 eV which is attributed to an InAs wetting layer∼2 ML in thickness. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119609

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The room temperature shot noise of a resonant tunneling diode was determined from microwave measurements as a function of bias. An AlAs/GaAs structure with multiple quasibound well states and asymmetric barrier thicknesses was investigated over a bias regime exceeding the first resonance. In contrast to results for single well state devices, significant noise suppression below the classical limit was also observed for bias ranges beyond the first resonance level. This suppression can be explained by competition between the first and second resonance levels for the thick barrier on the emitter side and due to predominately single barrier tunneling in the reverse polarity. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119599

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Nearly strain freeCuGaSe2andCuAlSe2thin films were successfully grown by metalorganic vapor phase epitaxy onCuGa0.96In0.04Se2substrates prepared by the traveling heater method (THM).CuAlSe2(112) epilayers exhibited fine surface structures which reflected the crystal geometry. TheCuGaSe2epilayers exhibited intense near-band-edge emission even at room temperature. THM-grown single crystals were demonstrated to be a suitable substrates for epitaxy of chalcopyrite compounds. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119600

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In several Tl- and Hg-based high-Tcsuperconducting materials, vortex-pinning defects were formed by irradiation with 0.8 GeV protons. The protons cause heavy constituent nuclei (Tl, Hg, Bi, &ellip;) to fission, which generates randomly oriented tracks. These columnar defects lead to significant enhancements in the current-conducting properties. We investigated bulk materials and thin films, irradiated with or without Pb or Au “amplifier foil” overlayers, which increase the number of column-creating fission fragments. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119601

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Switching fields of magnetic elements with nanometric dimensions have been investigated by Lorentz microscopy using a transmission electron microscope. Acicular elements of Co andNi80Fe20were fabricated by electron beam lithography and lift-off techniques. They were 1.6–3.5 &mgr;m long, 200 nm wide, and 20–50 nm thick, with flat rectangular ends or triangular pointed ends, and were patterned in linear arrays with center-to-center spacing ranging from 7 &mgr;m to 250 nm. Switching fields and reversal behavior of the elements were found to depend strongly on the shape of the ends and, in a closely packed array, on element separation, thereby providing a way of controlling their magnetic properties. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119602

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Photothermal methods were used to monitor thermal effects related to magnetoresistance of epitaxial magnetic metallic multilayers, in a direction perpendicular to the layers, as a function of the applied magnetic field. Photothermal signal changes induced by thermal conductivity variations were modeled in order to determine the suitable experimental conditions according to the technique used. Both photothermal microscopy and mirage detection were successfully applied to such measurements. For the sample studied here, a magneto induced perpendicular conductivity variation of ∼6&percent; was determined. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119603

出版商:AIP    

年代:1997

数据来源: AIP