SU1213510A1 - Method of measuring rate of surface generation-recombination - Google Patents

Description

The invention relates to semiconductor technology and can be used to study the surface properties of semiconductors in semiconductor micro- and optoelectronics, in the manufacture and study of semiconductor devices, in particular radiation detectors, and sources of electromagnetic radiation.

The purpose of the invention is to increase the measurement accuracy by eliminating the current associated with the generation of charge carriers in the spatial charge region of the pm junction, the breakdown current of the pm junction caused by the formation of microplasma, and the surface leakage current by depleting the semiconductor volume with minor ones charge carriers under the action of an electric field.

FIG. Figures 1 and 2 show the dimensionless and experimental volt – ampere characteristics, respectively.

The dimensionless current-voltage characteristics (Fig. 1) are calculated for the crystal thickness and for different values of the dimensionless surface generation-recombination rate S (for curve 1 Oj for curve 2 0.2; for curve 3 1, OJ for curve 4 2, OJ for curve 5 5, OJ for curve 6 20.0, curve 7 — ohmic characteristic of a crystal).

FIG. 2 shows the experimental current-voltage characteristics in the exclusion mode. Curve 8 corresponds to a crystal with a low surface generation – recombination rate, curves 9–11 correspond to the same crystal in the order of increasing values of the surface generation – recombination rate on wide faces of the crystal, curve 12 is the ohmic characteristic of the crystal.

Primer p. A semiconductor wafer with dimensions of 0 ,,, 078 cm, thickness, d, comparable to the bipolar diffusion length, is made of p-type single crystal germanium with a specific resistance at room temperature PS; 40 Ω "cm and a residual impurity concentration see To the narrow ends of the plate make contacts one anti-lock, the other - omi15.

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chesky Anti-blocking contact is made by melting In on a germanium surface etched in perhydrol), ohmic contact is by melting Ino ggsGao, oo5 The diffusion length in the material under study is Lf) 0.25 cm. The wide faces of the plate are treated symmetrically. The change in the rate of surface generation-recombination is achieved by various processing of wide faces. The low rate of surface generation-recombination (ScvlO cm / s) is achieved by etching in boiling perhydrol (Hg.02), the maximum rate of surface generation-recombination (S 10 cm / s) is rough grinding, intermediate values of the rate-surface generation- recombination - by fine grinding or by deposition of gold from its aqueous solution on the surface under study.

Current-voltage characteristics (VAC) of the crystals under study are measured at room temperature. Measurements are carried out in a pulsed mode. Pulse duration

30 (| c 150-600 μs) is chosen so as to avoid heating of the crystals and at the same time ensure the stationarity of the exclusion process. Current and voltage pulses

35 send a C7-12 stroboscopic oscilloscope. WAH is recorded on an LC4-003 recorder.

FIG. 2 shows the IVC in the exclusion mode. The ohmic characteristic (curve 5) is recorded after 0.2 µs from the beginning of the pulse, when an exclusivity has not yet arisen in the sample. Curve 1 corresponds to the sample with a low surface speed.

45natal generation-recombination. The exclusivity begins in this sample from very low voltages, the resistance of the specimen at the exclusion site increases 50 times over

50 compared with the original. Curves (.

2–4 correspond to the same sample in the order of an increase in the magnitude of the surface generation – recombination rate on wide grains of crystals. The presented IV characteristics have the form (fig. 2) characteristic for exclusion, at small voltages they are linear and coincide with them3

chesky characteristic. At medium voltages x U, the current is I l / U, P is large voltages x i. Determining the resistance of the crystal in the linear region in terms of complete exclusion Rjic of the cutoff voltage dp of curves 1–4, the values of the surface generation – recombination rates are calculated using the formulas proposed. So, for curves 1-4 S “75; 580; 8-10 4,3 "jxlO cm / s, respectively. Values

(Calculated from the resistance of the crystal in the full exclue mode, differ from the values calculated from the cut-off voltage, within 5%

Experimentally, the proposed and known methods are compared under the same measurement conditions, on one specific material, using the same manufacturing technology. The comparison is carried out on the cris. Talla Ge. To crystals-Ge (p. S: x40 ohm-cm), which is used in the proposed example, is made

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floatable p-h junction in the same way as anti-blocking. Then, saturation current is used to calculate surface generation-recombination rates for various surface treatments and compare with similar ones obtained by the proposed method. Changing the value of surface generation-recombination rates is realized by precipitating gold from its aqueous solution at the same time as dp of the proposed method and for manufactured p-and-junction. Therefore, we can assume that the measured rates of surface generation – recombination in the proposed and known methods are the same.

The known method is sensitive to the magnitude of the velocity of the surface

20 cm / s recombination generation, while the proposed method makes it possible to measure cm / s, while the surface generation-recombination rate value is controlled by the third independent method.

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Compiler N.Vorobyov Editor N.Gunko Tehred S.Migunova Proofreader M. Samborska

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VNIIPI USSR State Committee

for inventions and discoveries P3035, Moscow, Zh-35, Raushsk nab., 4/5

Branch ram Patent, Uzhgorod, -ul. Project, 4

Claims (1)

METHOD FOR MEASURING SPEED · SURFACE GENERATION-RECOMBINATION, including measuring the current-voltage characteristic in the contact depletion mode of a semiconductor crystal by charge carriers, characterized in that, in order to increase the accuracy of the measurements, a semiconductor crystal with at least one anti-gate contact with the end face and thickness with the diffusion length of the charge carriers, the resistance of the semiconductor crystal or the cut-off voltage is determined by the measured current-voltage characteristic in exclusion mode and determining the rate of surface recombination of lasing by the following formulas: where S is the surface generation-recombination rate; D is the bipolar diffusion coefficient; , £ - dimensionless coefficient ’, β - dimensionless coefficient d - half crystal thickness * Н - dimensionless coefficient; Vack - crystal resistance in the full exclusion mode; Roh is the initial crystal resistance; 'Y - dimensionless coefficient; Watts - cutoff voltage; At _ek - voltage exclusion; K is the Boltzmann constant; T is the temperature; B is the length of the crystal; And; · is the concentration of electrons in an intrinsic semiconductor *, M - bipolar diffusion length; Ν 'is the concentration of “uncompensated impurity *, is the charge of an electron. SU ... 1213510> half-pro be