摘要:

An ensemble Monte Carlo (EMC) simulator has been used to study bipolar transport in siliconp+nandpn+homojunctions under forward-bias conditions, both in low- and high-injection regimes. The study focuses on a microscopic analysis of voltage fluctuations in such devices. The method of voltage-noise operation mode provides spatial analysis of the spectral density of voltage fluctuations under constant-current conditions. In the low-frequency range, the presence of shot, thermal, and excess noise due to hot carriers was found when the bias conditions were modified. Also, the EMC method permits ready evaluation of the noise equivalent temperature in both structures from the observed voltage fluctuations. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120554

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Likely contamination of GaN films by impurities emanating fromAl2O3,SiC, and ZnO substrates during growth has been studied by secondary ion mass spectrometry (SIMS) analysis. The defective near-substrate region allows impurities to incorporate more readily as compared to the more perfect crystal as evidenced by increased impurity levels in that region detected by SIMS. The SIMS measurements in GaN layers grown on SiC, ZnO, and sapphire showed large amounts of Si, Zn, and O, respectively, within a region wider than the defective near-substrate layer pointing to the possibility of impurity diffusion at growth temperatures. The qualitative trend observed is fairly clear and significant. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120343

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In situboron-doped polycrystallineSi1−xGex(x>0.4)films have been formed on the thermally grown oxides in a rapid thermal chemical vapor deposition processor usingSiH4-GeH4-B2H6-H2gas system. Our results showed thatin situboron-dopedSi1−xGexfilms can be directly deposited on the oxide surface, in contrast to the rapid thermal deposition of undoped silicon-germanium(Si1−xGex)films on oxides which is a partially selective process and requires a thin silicon film pre-deposition to form a continuous film. For thein situboron-dopedSi1−xGexfilms, we observed that with the increase of the germane percentage in the gas source, the Ge content and the deposition rate of the film are increased, while its resistivity is decreased down to 0.66 m&OHgr; cm for a Ge content of 73&percent;. Capacitance-voltage characteristics ofp-type metal-oxide-semiconductor capacitors withp+-Si1−xGexgates showed negligible polydepletion effect for a 75 Å gate oxide, indicating that a high doping level of boron at the poly-Si1−xGex/oxideinterface was achieved. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120344

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A substantial reduction of leakage currents during voltage sweeps from 0 to+20 Vis observed for overlap capacitors with polycrystalline silicon (polysilicon) capacitor plates and thermalSiO2as an insulator. The responsible electrical passivation has a high thermal stability and is localized at the sharp corner, where the upper polysilicon wraps over (overlaps) the lower polysilicon. From baking and recycling electrical-sweep experiments, we conclude that: (1) stability of the localized electrical passivation comes from electrons trapped at deep neutral oxide traps, (2) more than one trap binding energy is involved, and (3) thermal activation energies for electron detrapping, with estimated magnitudes up to 1.3 eV, are about three times larger than previously reported. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120345

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electron field emission from an array of micro-patterned monolithic diamond tips with varyingsp2content has been systematically investigated. The experimental results show that the field emission characteristics can be improved and the turn-on electric field can be reduced more than 50&percent; by increasingsp2content. Two hypotheses are proposed as an explanation of the effect ofsp2content on the field emission characteristics of diamond tips: the lowering of the work function due to defect-induced band generated bysp2content in the diamond lattice and an increase in the field enhancement factor due to embeddedsp2–diamond–sp2cascaded microstructures. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120346

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Lateral gettering is implemented in thin-film silicon-on-insulator (TFSOI) substrates by introducing crystalline defects in the vicinity of metal-oxide-semiconductor device channel regions prior to gate oxidation. As a result of the gettering a significant improvement in gate oxide integrity is achieved, with increased oxide breakdown voltages and charge-to-breakdowns, as well as a reduction in localized oxide charge trapping. The same gettering effect on separation-by-implantation-of-oxygen and bonded silicon-on-insulator substrates suggests that the lack of effective gettering is mainly responsible for the oxide degradation regardless of the TFSOI type. This work also demonstrates the feasibility of achieving bulk-comparable gate oxides on TFSOI substrates. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120347

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

When two hydrogen-passivated silicon surfaces are placed in contact under cleanroom conditions, a weak bond is formed. Cleaving this bond under ultrahigh vacuum (UHV) conditions, and observing the surfaces with low energy electron diffraction and scanning tunneling microscopy, we find that the ordered atomic structure of the surfaces is protected from oxidation, even after the bonded samples have been in air for weeks. Further, we show that silicon surfaces that have been cleaned and hydrogen-passivated in UHV can be contacted in UHV in a similarly hermetic fashion, protecting the surface reconstruction from oxidation in air. Contact bonding opens the way to novel applications of reconstructed semiconductor surfaces, by preserving their atomic structure intact outside of a UHV chamber. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120348

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have investigated the role of hydrogen in hydrogenated microcrystalline silicon (&mgr;c-Si:H) formation using hydrogen plasma treatments, in particular examining the possibility of subsurface reaction due to permeating hydrogen atoms, which leads to the crystallization of hydrogenated amorphous silicon (a-Si:H). It is demonstrated that the hydrogen plasma treatment ofa-Si:Hfilm on the anode using a cathode covered bya-Si:Hfilm, which is inevitably coated during the deposition period, gives rise to the deposition of&mgr;c-Si:Hover thea-Si:Hlayer, i.e., chemical transport takes place. It is also found that the pure hydrogen plasma treatment using a clean cathode induces only etching of thea-Si:Hlayer. These results imply that the present hydrogen plasma condition does not cause crystallization ofa-Si:Hbut only etching, and that careful experimentation is required to determine the real subsurface reaction due to atomic hydrogen. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120324

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The controlled synthesis of PbSe nanocrystal quantum dots with narrow size distributions was achieved through phase decomposition of the PbSe solid solution in a phosphate glass host. Structural characterization by electron microscopy and x-ray diffraction shows that the dots have mean diameters between 2 and 15 nm. The exciton Bohr radiusaB=46 nmin PbSe, so these quantum dots provide unusual and perhaps unique access to the regime of strong quantum confinement. The optical absorption spectra are compared to the predictions of a theoretical treatment of the electronic structure. The theory agrees well with experiment for dots larger than∼7 nm,but for smaller dots there is some deviation from the theoretical predictions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120349

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Electronic structures of Ag–As–Se glasses, which possess ion-hole mixed conduction, have been studied using a scanning tunneling microscope operating in tunneling-spectroscopy modes. The tunneling spectra show marked dependence on the scan speed of tip voltage. This scan-speed dependence appears to be caused byAg+-ion migration which is induced by electric fields generated by tips. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120350

出版商:AIP    

年代:1997

数据来源: AIP