摘要:

This article investigates steady-state nonequilibrium conditions in metal–oxide–semiconductor (MOS) capacitors. Steady-state nonequilibrium conditions are of significant interest due to the advent of wide-gap semiconductors in the arena of MOS (or metal–insulator–semiconductor) devicesanddue to the scaling of oxide thickness in Si technology. Two major classes of steady-state nonequilibrium conditions were studied both experimentally and theoretically: (i) steady-state deep depletion and (ii) steady-state low level optical generation. It is found that the identification and subsequent understanding of steady-state nonequilibrium conditions is of significant importance for correct interpretation of electrical measurements such as capacitance–voltage and conductance–voltage measurements. Basic implications of steady-state nonequilibrium conditions were derived for both MOS capacitors with low interfaces state densityDitand for oxide semiconductor interfaces with a pinned Fermi level. Further, a photoluminescence power spectroscopy technique is investigated as a complementary tool for direct-gap semiconductors to studyDitand to monitor the interface quality during device fabrication. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365343

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We propose an all-optical limiter based on the thermally induced intervalley transfer of electrons from&Ggr;-valley states with forbidden normal-incidence intersubband interactions to L-valley states which absorb strongly. Detailed modeling of the device performance in the short-pulse regime(⩽100ns) yields that the output intensity for a limiter with only 10&percent; insertion loss at low excitation levels will remain clamped over a dynamic range of 25–40.

ISSN:0021-8979    

DOI:10.1063/1.365344

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The operational principle of a new type p-i-i-n color sensor is described with the aid of numerical modeling. The modeling results account for the color detection mechanism recently presented that this kind of structure exhibits [T. Neidlinger, M. B. Schubert, G. Schmid, and H. Brummack, inAmorphous Silicon Technology—1996, edited by E. A. Schiff &etal; (Materials Research Society, Pittsburgh, 1996), p. 147]. By band gap engineering the experimental red response is maximized at larger reverse bias voltage whereas the green response has its maximum at low reverse bias voltage. The numerical modeling qualitatively reproduces the characteristic shape of the steady-state current-voltage curves at different illumination wavelengths. At low and at high reverse bias voltages the influence of the internal variables and parameters is identified and leads to the experimentally observed response. The potential profile of the p-i-i-n structure is of crucial importance to the color detection mechanism. At larger wavelengths the large potential drop across the two highly defective front layers assists recombination in the back part of the device, which thus leads to the drop in the red response at low reverse voltage. For the voltage-dependent shift in spectral sensitivity it is important that photogenerated carriers under green bias illumination are lost by recombination in the front part of the device. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365345

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An electrical system based on a tapered microelectrode has been developed for generation of high voltage sub-microsecond discharge in physiological medium. Different types of the resulting pulses of current are investigated as well as the dynamics of the associated cavitation bubbles. A highly localized zone of power dissipation—about 20 &mgr;m in size—results in a low threshold energy of cavitation bubble generation—about 3 &mgr;J—in comparison to laser-based intraocular microsurgical instrumentation with fiber delivery systems. Cavitation bubble dynamics resulting from the electric discharge is similar to that observed with ns-pulsed fiber-delivered lasers in strongly absorbing liquid medium. Efficiency of the pulse energy conversion to the bubble energy is about 12&percent;, which is lower than the best results obtained with lasers. In spite of that, due to the low threshold energy, cavitation bubbles required for effective cutting of soft tissue can be generated at energies lower than that used in laser instrumentation with fiber-based delivery systems. The proposed device has a potential to become a convenient and a cost-effective alternative to such lasers in vitreoretinal microsurgery. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365346

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The formation of amorphous layers in GaAs during ion bombardment at elevated temperatures, where dynamic annealing of radiation-induced defects is substantial, is shown to be extremely sensitive to the implantation temperature. For example, we have found that a temperature change of only 6 °C can change the residual damage from small clusters barely visible by conventional transmission electron microscopy and Rutherford backscattering to a thick amorphous layer. The temperature at which this occurs is strongly dependent upon the ion flux. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365347

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The surface of silicon in hydroflouric acid (HF) is coated with covalently attached hydrogen (SiHxgroups, withx=1,2,3), with probably a very small concentration of SiF bonds. In contrast with a recent claim by Niwano &etal; [J. Appl. Phys.79, 3708 (1996)], we show that the concentration of SiF bonds is as yet beyond infrared detection limits. Our analysis indicates that the band at2230 cm−1observed by these authors actually arises from electrolyte absorption. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.365348

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electrical characteristics of 4H-SiC depletion-mode junction field-effect transistors (JFETs) have been measured over an extended temperature range from 218 to 673 K. A basic model has been applied to predictI–Vcharacteristics for SiC JFETs over this extended temperature range using the standard abrupt-junction long-channel JFET equations. The model employs a two-level donor ionization structure using ionization energies of 0.050 and 0.080 eV and assumes a two-step inverse power law dependence of mobility on temperature based on recently published Hall measurement data. The modeledI–Vcharacteristics are in good agreement with the experimental data over the temperature range from 273 to 673 K. The deviations between the experimental data and the response model at the temperature extremes are attributed to increased substrate resistivity at 218 K and increased device leakage currents at 673 K.

ISSN:0021-8979    

DOI:10.1063/1.365349

出版商:AIP    

年代:1997

数据来源: AIP