Yu. V. Lisyuk

Voltage transient duration in a P-N junction at high injection levels

Formulas describing the final stage of the transient are obtained. The voltage-transient duration is shown to be substantially dependent on the diode base length.

Contactless RF methods for measuring electrophysical parameters of semiconductors

We review promising contactless radio frequency (RF) methods for performing localized diagnostics on semiconductors by using quasi-stationary devices. These are resonant systems operating in the frequency range from 100 kHz to 1 GHz that feature high spatial localization of the probe electromagnetic field in small geometrical volumes of the semiconducting samples. A properly chosen operating frequency provides both high spatial resolution and good conversion transconductance for the measured parameter, the detector signal for a wide range of materials with resistivities from 10−3 to 109 Ω·cm. We discuss the design of quasi-stationary devices for multiparameter, nondestructive, contactless monitoring of semiconducting ingots, wafers, and structures. We examine methods for measuring resistivity, mobility, and free charge-carrier lifetimes in semiconductors. We describe automated systems and instruments for nondestructive, contactless measurement of parameter distribution over the surface of semiconductor wafers and structures with a spatial resolution of 1 mm. We present the technical specifications of these instruments.

Dispersion of the permittivity of high-resistance semiconductors

We consider the mechanism of macroscopic polarization of semiconducting plates owing to the interaction of free carriers with an impurity level, in which role the level of the residual impurity of compensated semiconductors may appear. This mechanism, in combination with the diffusion-drift mechanism of polarization, results in additional dispersion of the real (ɛ′) and imaginary (ɛ″) parts of the dielectric permittivity, this being particularly significant for semiconductors of thickness ι smaller than the screening length Ls of free carriers. The character of the behavior of ɛ′ and ɛ″ depends on the relation between the Maxwell relation time τM and the times of carrier capture: τc and ejection τe by an impurity center. For τc≪τe≪tm and (ι/Ls) √τe/τc≫1 the dispersion of ɛ′ and ɛ″ is the same as for “thick” plates (ι/Ls≫1). For τc ≪ τm ≪τe and (ι/Ls)√τe/τc≫1 the ɛ″(ω) curve has a characteristic kink in the region ω ∿ 1/τe, indicating additional absorption associated with the ejection of carriers into the surface region.

Microwave power absorption in space-charge region of high-resistivity semiconductors

The distribution of a microwave electric field in the space charge region (SCR) of semiconductors is found from a joint solution of the diffusion-drift equation and the Poisson equation. Large enriching bends of the bands lead to screening of the microwave field by SCR free carriers, with the result that the microwave power absorption is limited when the bends become larger. An expression is found for the relation between the quality factor Qg of the capacitive gap of the measuring resonator and the size of the bends. Plots of maximum error of measurement of the conducitivity of semiconductors due to neglect of absorption in the SCR against measured values of Qg are obtained.

uhf Photoconductivity measurement at high excitation levels

A contactless method is described for measuring photoelectric properties of semiconductors at uhf, employing losses introduced in a resonator by photoconductivity. The possibility of experimental measurement of the filling coefficient of the working range of a uhf generator is demonstrated.

Polarization of a laser medium in which the molecules have a velocity-dependent mean free time

The polarization of a medium consisting of two-level molecules undergoing collisions with a velocity-dependent mean free time is found by a direct averaging, without the use of a kinetic equation.