摘要:

Room‐temperature optical bistability has been demonstrated in hydrogenated amorphous silicon at wavelengths greater than about 700 nm. Switching powers as low as 0.8 mW (switching intensities 1.7 kW/cm2) are observed. The measured switching times are found to be compound, with time constants from 50 &mgr;s to 1 ms.

ISSN:0003-6951    

DOI:10.1063/1.103183

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An acoustic microscope operating at 15.3 GHz and using superfluid4He as the coupling medium has been developed. The helium is colder than 0.9 K to achieve low acoustic attenuation, and is pressurized to greater than 20 bar to eliminate three‐phonon processes which saturate the received signal as the input power is increased. A resolution of 150 A˚ has been achieved.

ISSN:0003-6951    

DOI:10.1063/1.102603

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Particle‐in‐cell simulations of radio frequency glow discharges between parallel‐plate electrodes were performed to test the role of secondary emission at applied frequencies above the ion plasma frequency. With the secondary electron emission coefficient set to zero, the high‐energy tail of the electron energy distribution function in the center of the glow is modulated at the applied frequency, and these energetic electrons show substantial anisotropy. In addition, a pulse of ionization propagates across the glow, correpsonding to the directed velocity of the high‐energy electrons in the center of the glow. These high‐energy electrons originate at the plasma‐sheath boundary and appear to be the result of sheath heating.

ISSN:0003-6951    

DOI:10.1063/1.102604

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin germanium films on SiO2completely melted by pulsed laser irradiation cool rapidly by thermal conduction to the substrate until they solidify.Insitumeasurements indicate that the liquid is supercooled by 420–530 K with respect to the crystalline phase prior to solidification. Cross‐sectional transmission electron microscopy reveals nucleation events at the Ge/SiO2interface. The microstructure of these events is comprised of a very fine grained (5–15 nm) polycrystalline core with much larger grains extending laterally and toward the free surface. It is believed that nucleation of the amorphous phase, which was subsequently converted to the fine‐grained material, initiated solidification.

ISSN:0003-6951    

DOI:10.1063/1.103326

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Increasing the concentration of the carbon dopants inp‐GaAs layers grown on semi‐insulating substrates to levels of 1×1020to 5×1020cm−3enables the formation of an ohmic contact with low resistance using the refractory Pt/Ti metallization. These contacts showed ohmic behavior prior to any heat treatment with specific contact resistance as low as 7×10−6&OHgr; cm2(0.08 &OHgr; mm) for the lower doping level and 8×10−7&OHgr; cm2(0.04 &OHgr; mm) for the higher level. Small improvements in the specific resistance of the former contact were achieved by rapid thermal processing at a temperature of 450 °C for 30 s, which yielded a value of 4.9×10−6&OHgr; cm2. The electrical nature of the contact to the heavily doped GaAs was not affected by heat treatments at temperatures up to 450 °C. Rapid thermal processing of these contacts at higher temperatures, however, caused an increase in the contact resistance which was correlated to the expanded Ti/GaAs and Pt/GaAs interfacial reactions. Current‐voltage characteristics were found to be temperature independent. This suggested that the field emission quantum‐mechanical tunneling was the dominant carrier transport mechanism in these contacts.

ISSN:0003-6951    

DOI:10.1063/1.102605

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Improvement on the current‐voltage characteristics of polycrystalline silicon contactedn+‐pjunctions after they were applied a high‐field scanned stressing is reported. For the stressed diodes, the leakage current decreased as much as two orders, the breakdown voltage shifted from −45 to −60 V, and the forward ideality factor also decreased. Scanning electron microscopy photographs on the cross‐sectional view of the junctions revealed that local melting might have occurred during stressing to cause the improvement.

ISSN:0003-6951    

DOI:10.1063/1.102606

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new structure of a three‐terminal hydrogenated amorphous silicon/crystalline silicon (a‐Si:H/c‐Si) heterojunction switching device is successfully developed. The device can be controlled by a gate bias. The switching voltage, holding voltage, and switching current all increase with an increase of undopeda‐Si:H thickness. The electrical characteristics and switching phenomena of this device are discussed.

ISSN:0003-6951    

DOI:10.1063/1.102607

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report an investigation of trapped positive charge in as‐fabricated plasma‐enhanced chemical vapor deposited SiO2films using electrical and spin resonance techniques. We show that the positive charge results from donor‐like ‘‘slow’’ interface states (‘‘anomalous positive charge’’) rather than trapped holes, and that most (∼95%) of the positive charge is not related toE’centers. The positive charge is similar to that seen in electron‐injected thermally grown SiO2, and unlike radiation‐induced trapped holes.

ISSN:0003-6951    

DOI:10.1063/1.103327

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Epitaxial layers of GaAs have been grown by metalorganic molecular beam epitaxy (MOMBE) with atomic carbon concentrations ranging from 4×1017to 3.5×1020cm−3. The dependences of GaAs lattice parameter and hole concentration on atomic carbon concentration have been determined from x‐ray diffraction, Hall effect, and secondary‐ion mass spectrometry measurements. For atomic carbon concentrations in excess of 1×1019cm−3, the hole concentrations are less than the corresponding atomic carbon concentrations. Lattice parameter shifts as large as 0.2% are observed for carbon concentrations in excess of 1×1020cm−3, which results in misfit dislocation generation in some cases due to the lattice mismatch between the C‐doped epilayer and undoped substrate. Over the entire range of carbon concentrations investigated, Vegard’s law accurately predicts the observed lattice contraction.

ISSN:0003-6951    

DOI:10.1063/1.102608

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Current‐voltage, capacitance‐voltage, and internal photoemission measurements of back‐to‐back Schottky diodes of buried metal (Al,Ga)As/NiAl/(Al,Ga)As double heterostructures grown by molecular beam epitaxy are reported. By using a selective etch process to access the buried layers and fabricate three‐terminal devices, independent measurements of the barrier height on both sides of the buried metal double heterostructure were performed. Schottky diode behavior was observed for both upper and lower diodes and the barrier height was measured to be 1.1 eV for both diodes using internal photoemission. Electrical measurements showed a lower effective barrier height for the upper metal‐semiconductor interface as compared to the lower interface in agreement with the different defect densities in these heterostructures.

ISSN:0003-6951    

DOI:10.1063/1.102609

出版商:AIP    

年代:1990

数据来源: AIP