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An ab-initio calculation of the structure and electron-spin properties is performed for the Zn-P complex in Si, which is considered to be a part of the ZnPSi15H22 cluster. The distribution of electron-spin density is calculated over the Zn, P, and Si atoms of the cluster. Comparatively high spin densities are found to occur at 1Zn, 2Si, and 13Si. The interatomic distances in the cluster are determined. ESR spectroscopic characteristics of the Zn-P complex are evaluated by computer simulation on the basis of previous experimental results. The ESR data obtained indicate a complicated nature of the spin exchange between the two paramagnetic centers.

A method is proposed for counting small numbers of impurity paramagnetic centers in semiconductor specimens. It involves SQUID measurement of static magnetic susceptibility under resonant microwave saturation of the magnetic sublevels. The ultimate sensitivity of the method is calculated and compared with those of other approaches.

The structure is examined of the semiempirical relaxation operator R (a tensor of order 4) used to extend the quantum Liouville equation to nonequilibrium processes, particularly to the absorption of microwave quanta by a Zn-P two-spin paramagnetic system in silicon. The transition-matrix elements Mmn representing microwave absorption are directly involved in the modified quantum Liouville equation. The relaxation operator is expressed in terms of the transition rates vmn and the overlap functions pmn for the system: Rmjkn = vmjpkn + pmjvkn. It is assumed that the component representation of the relaxation operator is structurally similar to that of the Liouville operator Lmjkn in the sense that the former can be constructed from the latter by replacing ±iHmn and δmn with vmn, and pmn, respectively. This changeover reflects the stochastic nature of the interaction between the Zn-P system on the one hand and the surrounding silicon and microwave radiation on the other. A physical interpretation of the relaxation-operator components is proposed.

The progress of convective current instability associated with slow recombination waves in Zn-compensated P-doped Si is studied experimentally. The drift is examined of an excess-carrier pulse in specimens exposed to an electric field close to the recombination-wave threshold, the pulse being created by intrinsic photoconductivity. It is established that the pulse travels in the direction of the drift of long-lived carriers, electrons. The speed of the pulse is found to agree with a predicted value to within an order of magnitude. Oscillations are discovered in the trailing edge of the specimen photocurrent response; their period is found to be equal to that of self-sustained current oscillations caused by slow recombination waves. Time-dependent profiles of photocurrent response are obtained that are in qualitative and quantitative agreement with ones arrived at in an earlier computer simulation.

A computer simulation of the ESR spectra of a Zn-P two-spin system in Si is carried out, involving solving the quantum Liouville equation supplemented with a semiempirical relaxation operator (represented by a tensor of order 4). The mathematical model employed enables one to compute ESR spectra for continuous-absorption conditions as the paramagnetic-center density is increased. Two conclusions are drawn from a comparison of the simulated spectra and previously measured ones: (i) For a model of ESR spectra to be accurate it must include both the dipole-dipole interaction between the magnetic moments and isotropic and anisotropic (vector) exchange interactions. (ii) The interaction constants are comparable with one another and so cannot be neglected. The cases are covered of a triplet and a singlet state of the ion pair, the parameter values being the same; in the latter case, the system includes a spin-0 and a spin-1/2 nucleus with two valence electrons interacting by the dipole and exchange mechanisms. Satellite lines resulting from the interactions are observed in the simulated spectrum for an extremely small natural line width.

For slow recombination waves in Si:Zn, stationary intensity profiles along the specimen are measured with an SEM operated in the voltage-contrast mode. The main findings are as follows: (i) The intensity falls from a maximum with increasing distance from the cathode, where a stationary high-field domain is located, and almost vanishes far short of the anode. (ii) The intensity grows with specimen voltage. (iii) The voltage-contrast image for the highest specimen voltage displays oscillatory potential variation over the stationary high-field domain, indicating the stratification of electric field.

A nonlinear theory of recombination waves in semiconductors is constructed that addresses quasi-neutrality breaking in the electron–hole plasma with fully developed instability. It is established that with increasing applied electric field a recombination wave of uniform amplitude is transformed into a traveling solitary domain; the domain formation manifests itself in the transition from almost sinusoidal to relaxation oscillations of current. A formula is derived that relates the domain velocity to the properties of the material and the current–voltage characteristic of the specimen. The predicted transformation of recombination waves is verified by checking against previously obtained experimental results concerning slow recombination waves in Si specimens with Zn doping compensation. It is found that a calculated field at which relaxation oscillations arise agrees with the measured one. The frequency of relaxation oscillations is examined as a function of applied field on the basis of the theory and the experiment. The calculated characteristic is shown to be in qualitative and quantitative agreement with the measured one.

The generation and voltage dependence of a stationary high-field domain in Si : Zn about the excitation threshold of slow recombination waves are investigated by scanning electron microscopy. It is found that the domain arises at the cathode when the electric field in the specimen is about 10 V/cm. The field inside the domain and at its boundary (∼103 V/cm) considerably exceeds the average specimen field. The field in the domain linearly increases with dc specimen voltage but stays within the same order of magnitude. The domain linearly grows to approximately 100 μm with increasing dc specimen voltage. Domain generation is found to occur in passing from a linear to a sublinear portion of the specimen current–voltage characteristic.

An ESR investigation is conducted of P-doped, Zn-compensated Si single crystals. A narrow, faint peak is observed in the ESR spectra against the background of a broad, intense Lorentzian line produced by uniformly, randomly distributed Zn atoms. Examined at a finer magnetic-field resolution, the peak is found to contain a fine structure characteristic of a two-spin system in a triplet state. The two-spin system is identified as an isolated pair made up of a spin-0 neutral Zn atom and a spin-1/2 positively charged P ion. The atoms of the Zn-P pair are about 10 A apart, as the value of the dipole constant implies (the distance is twice the Si lattice spacing). As the temperature is lowered, the Zn-P peak grows in intensity relative to the Lorentzian line, whose intensity and width decrease. The changes in the Zn-P peak with temperature when this is below 183 K indicate a considerable increase in Zn/P interatomic distance. This is attributable to a phase transition in the neighborhood of the ion pair.