摘要:

Implanted ohmic contacts were made on molecular beam epitaxy grown GaN materials. Si was implanted at a doping density of about4×1020  cm-3to decrease the contact resistance of the contact, followed by an activation anneal at 1150 °C for 30 s. The overlay metal Ti/Au was evaporated. Four-probe measurements were performed on transmission line model patterns. The measured maximum contact resistance was 0.097&OHgr; mm and the apparent specific contact resistance was3.6×10−8&OHgr; cm2.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118182

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

High quality wurtzite GaN epilayers have been grown on ZnO(0001) substrates by reactive molecular beam epitaxy. Photoluminescence and reflectivity measurements point to high quality presumably due to the near match of both the crystal lattice parameter and the stacking order between GaN and ZnO. In addition, the good films lack the characteristic yellow photoluminescence band. Any misorientation of the GaN epilayer planes with respect to the ZnO substrate is not detectable with polarized reflectivity. The x-ray double crystal diffraction measurements indicate this misorientation is much smaller than those for GaN epilayers on SiC andAl2O3 . ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118183

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report visible (380–650 nm) electroluminescence from reverse-biased siliconp-njunctions and fromn-andp-type field-effect transistors designed for a standard chip-fabrication process. We measured the spectra of over 40 junctions and devices and found that they differed from previously reported silicon electroluminescence spectra. We use a hot carrier recombination model and account for Fabry-Perot effects to explain the observed electroluminescence spectrum. Our model’s prediction is in good agreement with the measured spectra. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118184

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report an experimental study of the optical properties of island layers resulting from molecular beam epitaxial deposition of Ge on Si(111) substrates. The combination of electroreflectance spectroscopy of theE1transition and Raman scattering allows us to separately determine the strain and composition of the islands. For deposition at 500 °C a deposited layer of 1.36 nm of Ge assembles into 80 nm diameter islands 11 nm thick. The average Si impurity content in the islands is 2.5&percent; while the average in-plane strain is 0.5&percent;. Both strain and Si impurity content in islands decrease with increasing Ge deposition. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118169

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple technique to measure the minority carrier mobility using a bipolar junction transistor is demonstrated. By fixing the base-emitter voltage, the carrier injection into the base is constant. The collector current is then monitored as a function of a magnetic field applied perpendicular to the current transport across the base. The magnetic field leads to an increase in base transit time and a corresponding decrease in collector current. From the resulting fractional change in collector current, the minority carrier mobility in the base can be determined. For narrow base transistors, quasiballistic transport across the base must be taken into account when determining the bulk minority carrier mobility. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118185

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ce activatedSrGa2S4blue emitting phosphors were examined using electron paramagnetic resonance and x-ray diffraction to determine the local environment and oxidation state of the Ce ion. Photothermal deflection and photoluminescence spectroscopies were applied to determine absorption and emission characteristics. It is found that the majority of theCe3+ions substitute for the eightfold coordinated antiprismaticSr2+cations in the structure. Our results show that the Ce ions exhibitC3hsymmetry; this suggests that they are ninefold coordinated. This coordination may arise from a nearby S interstitial, energetically favorable because of charge compensation. To achieve this symmetry, only minor rearrangements of the eight S atoms in the antiprismatic configuration are required. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118186

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Gated structures have been fabricated on the InAs/AlSb/GaSb system enabling the control of the relative electron and hole carrier densities in these type II crossed band gap structures. By using insulated gates, a wide gate voltage range, with very low leakage levels, is obtained, allowing the study of these systems from electron dominated transport through to hole dominated. Associated with this transition, a change from positive to negative transconductance is observed. Studies of the quantum Hall effect show features related to both electron and hole Landau level formation with the crossover from electron to hole dominated transport found to be a function of the perpendicular magnetic field. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118187

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

TheCdAl2S4single crystal grown by the chemical transport reaction method in an excess sulfur atmosphere showed the intensive blue photoluminescence (PL) peaked at 462 nm at 280 K. TheCdAl2S4single crystal had the defect chalcopyrite structure, and the optical energy gap of the single crystal with the direct band structure was found to be 3.398 eV at 280 K, and to be 3.577 eV at 17 K. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118188

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Semiconducting polymer heterostructures with strong two-dimensional quantum confinement of excitons are prepared by self-assembly of two conjugated polymers in binary blends. Exciton confinement effects in the semiconducting polymer quantum wires were observed at room temperature by photoluminescence excitation and photoluminescence spectroscopies and by electric field-induced photoluminescence quenching. Observation of new exciton states, enhanced luminescence, and stability of luminescence at high electric fields (3×106V/cm) confirmed the one-dimensionality of the excitons in the organic quantum wires. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118189

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ferroelectric heterostructures ofAu/Pb(Zr0.52Ti0.48)O3/SiO2/SiandAu/Pb(Zr0.52Ti0.48)O3/Sihave been fabricated by using laser ablation technique. Electrical properties of these ferroelectric field-effect transistors have been characterized through both the current vs voltage and capacitance vs voltage (C–V) measurements. The C–V characteristics ofAu/Pb(Zr0.52Ti0.48)O3/SiO2/Siheterostructures demonstrate a polarization switching behavior, showing a memory window as much as 1 V at 1 kHz. In addition, the experimental results reveal that aSiO2buffer layer is essential for memory properties in theAu/Pb(Zr0.52Ti0.48)O3/SiO2/Sigate structure. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118190

出版商:AIP    

年代:1997

数据来源: AIP