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December 31, 1967
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27948 S/185/60/005/004/007/021 Effect of the external electric... D274/D306 for a sinole surface state only. As the- germanium and silicon surfaces have 4 frist st.-ites, it is of i-aterest to generalize John- Soli's formula for any nLI(Rl)cr of states. Vs is determined from vs y @z- W dY p e e dAp (2) where 6. i@ the relative increase in hole-concentration during ations one ob illum, ination of the specimen. @@fter some traisform- t ai ns ), -Y dY ?.@e +e -2 d A p + V (Ij where =@+I npit Tj >> I -X2 npll Tj< 1 (12) I + e-'Y-ln x+'j)1-2e- (1*-")'+Y. Card 5/8 27941*) S/185/60/005/004/007/021 i@fEect of tile external electric ... 1)274/D306 Formulas (2) and (11) determine the dependence of the photo-cmf V.S on the sijrf@ice potential and surface states. gigures are shown w1th theoretical and experir,'iental curves Vs(Y). It is noted that p the agreement bett..reen theory and experiment is good qualitatiVely only, whereas quantitatively there are discrepancies; these may be due to neglecting slow surface states, arid to errors in deter- atining the surfac potential and s urface states. Further, the dro-@) is consic1cred in the capacitor photo-emE vhich depends on ZS., For silicon, the time constants '),' p arid -C are not only-of diff- erent magnitude (in the absence of an external field), but tlicir depc-ndence on Y is of a different character too. It is likely that the -@`orriation of a D-n junction at the silicon. surf ace hin- ders the relaxation of the Dhoto-emf. The i:iagnitude of 'r is P . The determined by diffusion processes and surface recombination surface conditions (zone bucklinor and surf ace states) have a con- siderable effect on the photo-emf of silicon and -rcrmanium. The surface potential Y can be determined in principle by compariug experimental and theoretical values of V pM and V p(Y). But such Card 6/8 2 /18 51601005/0 /0 0 7/0 2 1 Ef Ilect (,f the external cLectric D274/D306 OR) Instvtlit lizyl,:y A' Ul'Si-,, (PhVsics Institute z@,S Ukrs" ',;o-,-7e7..bcr 5, 1959 Card 8,,/8 89270 S/1 21/61/003/OD1/002/OZ'T2 B1 02/B21 2 f 4/30 0 AUTHORS: Primachenko, V. Ye. and Snitko, 0. V. TITLE: The role of a dielectric in investigations of the field effect in semiconductors PERIODICAL: Fizika tverdogo tela, v. 3, no. 1, 1961, 15-18 TEXT: One of the most important methods used to study the surface properties of semiconductors is the method of the field effect (change of the surface conductivity under the influence of an external electric field@ here the semiconductor is a capacitor plate which is covered with a di- elec;ric (mica, strontium titanate) to increase the breakdown voltage. Therefore it is of interest to know the effect of the dielectric on the surface properties of the semiconductor; several studies made for this purpose (among others, by Shao and Morrison) are briefly discussed in the introduction. In the following, the authors report on their own experi- ments. First, they repeated the experiments of Shao and found that a considerable charge remains on the mica after the electrode has been removed iinter voltage. Then,experiments have been undertaken to measure Card 1/5 89270 S11 81/61/OD3/001/002/042 The role of a dielectric in... B102/B212 the field effect and the capacitor photo-e.m.f. directly, with and without mica, in a vacuum and in air. These experiments were made with n- and p-type Ge and n-type Si. As the results obtained were similar, only those concerning the n-type Ge (1.- 28 ohm-cm, thickness 340 @L) are discussed. Fig. 1 shows the change of the conductivity AT and the capacitor photo-e.m.f. V , measured for 15 seconds after a constant field had been applied, as a @unction of the capacitor charge (Q=CV); C with mica has 25 p+LF, without mica, 10.5 ppF. Fig. 2 illustrates the long-period relaxation effect of the field for various cases. It is demonstrated again that curves recorded with and without mica coincide in dry air and in a vacuum, while those recorded in humid air deviate considerably from each other. Relaxation is more rapid wit mica. All experiments showed consistently that in fields up to I- 2-10@ v/cm, no charges are transferred from the semiconductor to the dielectric in dry air and in vacuo. Results obtained for humid air are indicative of a partial charge transfer to mica, which increases with humidity; this is related to the surface conductivity of mica in humid air. There are 2 figures and 9 references: 6 Soviet-bloc and 3 non-Soviet-bloc. Card 2/0 SNITKO" 0. kwid.fiz.-matem.nauk , I I -------- - - SemiconductorS. Nauka i zhyttia 11 no-3:25-27 Rr 162. (MIRA 15.8) (Semiconductors) S/181/62/004/010/045/063 B102/B112 AUTHORS: Primachenko, V. Ye., Litovchenko, V. G., Lyashenko, V. I., and Snitko, 0. V. --Vty carrier adhesion on.the silic'bn surface TITLE: Minor PERIODICAL: Fizika tverdogo tel4, V. 4, no. 10, 1962, 2925-2930 0 TEXT: This paper is aimed to show that under certain conditions a charge accumulation may occur on the silicon surface and that the bipolarity (,@In - 6p) may be disturbed. This is, however, contradictory to the observations made by other authors (see e.g. Phys.Rev.101, 1272, 1956; Semic.Surf.Phys.,85,1957). The disturbance of bipolarity of the intrinsic photoconductivity observed is attrAu 'ted to minority carriers accumulating on fast surface levels. The same method of investigation was used as described in previous papers (FTT 1,980,1959; FTT 2, 5911 1960; UFZh,5,345,1960). The specimens were n-type Si single crystal platelets 200-400g thick with resistivities of 30 - 200 ohm-cm and volume lifetimes of - 1000gsec, the surfaces of which had been etched with CP-8. in germanium the bipolarity-o@f the surface photocurrent may be disturbed Card 1/3 S/181/62/004/010/045/063 Minority carrier adhesion on ... B102/B112 only at low temperatures, but in etched silicon it may be disturbed even at room temperature. This is proved (1) by the.nature of the photo- conductivity relaxation of thin samples if the oscillogram shows two exponents with widely differing time constants;.(2) by the constant T sh of the short-term photocurrent component being inversely proportional to the electric field aDDlieds whereas the constant of the long-term component is independent of it; (3) by the fact that the long-term component can be caused to vanish by the usual method of trap filling; (4) by the long-term component increasing as the temperature decreases, while the short-term component decreases and almost vanishes completely, this being related to the intensified charge accumulation; in both cases ln-r = f(l/T) follows a linear course4 (5) by the results obtained in a study of the kinetics of the field effect also indicating a disturbance of bipolarity. This bipolarity is also indicated by the field dependence 0 .0 r sh and -r1and (7) it is particularly pronounced in samples kept on air for a longer period of time after they had b 'een etched. (8) Experiments on the condenser photo-emf proved that the disturbance of the photocurrent bipolarity of Si is related to a change'in the surface charge. Such,a Card 2/3 S/181/62/004/010/045/063 Minority carrier adhesion on B102/B112 disturbance occurs when Cn exp Etv- p ne