Nontrivial capacitance behavior, including a negative capacitance (NC)
effect, observed in a variety of semiconductor devices, is discussed
emphasizing the physical mechanism and the theoretical interpretation of
experimental data. The correct interpretation of NC can be based on the
analysis of the time-domain transient current in response to a small voltage
step or impulse, involving a self-consistent treatment of all relevant physical
effects (carrier transport, injection, recharging etc.). NC appears in the case
of the non-monotonic or positive-valued behavior of the time-derivative of the
transient current in response to a small voltage step. The time-domain
transient current approach is illustrated by simulation results and
experimental studies of quantum well infrared photodetectors (QWIPs). The NC
effect in QWIPs has been predicted theoretically and confirmed experimentally.
The huge NC phenomenon in QWIPs is due to the non-equilibrium transient
injection from the emitter caused by the properties of the injection barrier
and the inertia of the QW recharging.Comment: 9 pages, Latex, 11 ps figures; to be published in IEEE Trans. on
Electron Device
A new type of thin-film polarizing beam splitter (PBS) is proposed that is based on the effects of light interference and frustrated total internal reflection. This PBS has a significantly better performance than conventional thin-film PBS's. It is nonabsorbing, broadband, and wide angle and has high extinction ratios in both the transmitted and the reflected beams. The principles and theory of this PBS are described in detail. Several PBS's designed for the visible and the infrared spectral regions are described. The measured results for a prototype visible PBS of this type are presented as well.
A method is described for the design of a thin-film all-dielectric polarizing beam splitter in which the transmittances for p- and s-polarized light are greater than 0.96 and less than 0.03, respectively, throughout the spectral region extending from 0.40 to 0.70 µm, and for an angular field of 12° measured in air.
Several different thin-film design problems were solved by the comprehensive-search, gradual-evolution, minus-filter, flip-flop, and inverse-Fourier-transform, thin-film synthesis methods. In order to compare the relative effectiveness of each method, the results obtained and computation times required by these techniques for primary, intermediate, and final solutions are given.
A method for the design of cutoff filters is proposed that is based on the use of light at nonnormal angles of incidence and on the use of coating materials with a large dispersion of the optical constants. The optical constants are presented of several films made from indium tin oxide--a material that satisfies this requirement. The filtering is due to absorption, critical angle effects, or both. The theory of this type of filter is described, and the calculated performance of two long-wavelength cutoff filters based on the use of indium tin oxide films is given. The angular performance and the producibility of one of these filters are examined. Some applications for these filters are considered, and the feasibility of producing similar filters for other spectral regions is discussed.
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