ISSN: 35-38 Vol. 4, Issue, December 7 Some prmeters of vricps with grdient bse re bsed on Shottky brrier Mmtkrimov O.O., KuchkrovB.Kh. Rector, Nmngn engineering-technology institute, Kosonsoy str.,7, Nmngn, Uzbekistn Senior techer, Nmngn stte university, Uychin str.,36, Nmngn, Uzbekistn ABSTRACT: The volt-frd dependence of vricpe mde on the bsis of Schottky brrier subjected to comprehensive hydrosttic compression up to 6 kbr is considered, s well s cpcitnce vritions from the voltge s the frequency increses from 44 Hz to 5 khz. A strong dependence of the brrier prmeters on the shpe of the impurity distribution profile nd on the pplied pressure is shown. It is estblished tht holding the vricp within minutes under pressure of 6 kbr leds to n increse in its sensitivity. I. INTRODUCTION In modern microelectronics, lyered heterogeneous structures of the metl-insultor-semiconductor (MIS) type re widely used. They form the bsis of most discrete semiconductor devices nd integrted circuits. Therefore, the ctul tsk of microelectronics is to improve the prmeters nd chrcteristics of semiconductor MIS devices nd elements of integrted circuits.there re vrious wys to solve this problem, including improving methods for mnufcturing dielectric films, improving the qulity of the interfce between semiconductor nd dielectric film, using new, more promising mterils tht re suitble for use in thin-film stte nd mking it possible to expnd the functionlity of instruments. The most widely used dielectric in the mnufcture of MIS structures is currently silicon dioxide, since it is the nturl oxide of the semiconductor substrte, which forms the bsis of most semiconductor devices nd elements of integrted circuits. In modern devices of semiconductor microelectronics, the ctive instrument re is very thin semiconductor lyer, ner-surfce region, or boundry between two medi.mis structures re convenient test objects, both for controlling technologicl processes, nd for elucidting the mechnisms of electronic processes occurring in the nersurfce lyers of semiconductor nd dielectric under vrious externl influences []. One of such MIS devices s test objects re electric cpcitors with cpcitnce controlled by the pplied voltge - vricps [,3]. Vricps bsed on MIS system cn be used in electronic devices of the RF nd microwve rnges [4] to control the frequency nd phse of n lternting signl, s well s for frequency multipliction. At present, the bsic element of microwve phse shifters is the p-i-n-diode [5]. The development of vricp on the bsis of the MIS system for these purposes provides the principl possibility of reducing the control power. Despite the wide vriety of existing designs of vricps bsed on Schottky diodes, p-n junctions, metl-insultor-semiconductor structures, ech of them hs vrious drwbcks nd limittions. II. DESCRIPTION AND RESULTS OF THE RESEARCH When creting vricps for more efficient opertion, the condition of non-uniformity of the volt-frd chrcteristic [6-9] is necessry. To obtin sufficiently lrge unevenness of the chrcteristic, shrp profile of the impurity distribution concentrtion in the bse region is used. A predetermined impurity concentrtion profile is obtined using epitxil growth processes. However, it is known tht bric effect on both the originl semiconductor substrte nd the formed Schottky brrier leds to chnge in the impurity distribution [], which cn be used in the mnufcture of vricps. Copyright to IJARSET www.ijrset.com 56
ISSN: 35-38 Vol. 4, Issue, December 7 An importnt property of brrier cpcitnce of vricps is its prcticl lck of inerti. The chnge in the brrier cpcitnce of MIS structure with Schottky brriers with chnge in the pplied voltge is due to the displcement of the min chrge crriers in the regions djcent to the brrier lyer. The rte of this process is very high, since the exchnge-chrge time in this cse is determined by the Mxwell relxtion time M, where is dielectric qn permebility, q is the electron chrge, n is the electron concentrtion, ndis their mobility. -4 s. For silicon, this vlue is pproximtely five times greter. For exmple, for GAs, n = 7 cm -3 This mens tht vricps must remin opertionl even in the submillimeter rnge (t frequencies up to Hz higher) [] In this pper we consider the current-voltge dependence of the Schottky brrier, for the cse when the impurity concentrtion in semiconductor substrte vries ccording to the lw n( x) n / x where n is the impurity concentrtion in the semiconductor t the interfce with the metl, is the constnt, nd x is the coordinte reckoned from the metl-semiconductor interfce into the depth of the semiconductor. Using the Poisson eqution nd the dependence of the density of the spce chrge on x, we obtin: d en dx x () After integrtion over the coordinte, we hve: d en dx rctn( x / ) c () To find the constnt in eqution (), we use the following boundry conditions x L, d / dx, ; x, K, d / dx, where is the contct potentil difference between the metl nd the semiconductor. Using these boundry conditions, we get the vlue: en rctn( L / ) c Substituting expression (3) into eqution (), we obtin: (3) d en rctn( x / ) en rctn( L / ) dx (4) After integrting expression (4) with respect to the coordinte, we hve: en x rctn( L / ) x rctn( x / ) en ln[ ( x / )] ( x) c (5) After determining the constnt c c en ln[ ( L / )] (6) Copyright to IJARSET www.ijrset.com 57
ISSN: 35-38 Vol. 4, Issue, December 7 we hve: en xrctn( L/ ) xrctn( x / ) en ln[ ( x / )] ln[ ( L / ( x) )] (7) nd then we find the depth of penetrtion of the electric field into the semiconductor ( U) L exp en K / (8) It is seen from the expression obtined tht the dependence L = L (U) differs significntly from tht clculted for the uniform distribution of the impurity [6,7]. Considering the cpcitnce of the metl-semiconductor contct in the flt-cpcitor pproximtion, we find the dependence of the cpcity of the Schottky diode on the pplied voltge (Figure ) for different vlues of the prmeter ( -6, 4-6, 6-6, 8-6 ). From the dependence shown in Fig., it cn be seen tht the clculted voltge-voltge chrcteristic constructed for n Schottky diode of the Au-nSi type vries gretly depending on the vlue of the prmeter. When creting vricp, in order to increse the efficiency of their opertion, the condition of unevenness of the volt-frd chrcteristic [8] is necessry. Fig.. Clculted C-U dependences for the Schottky diode for vrious vlues of the prmeter Indeed, one of the chrcteristic prmeters of the vricp is its sensitivity: dc U S C du n (9) Here, n is the exponent in the expression N (x) = N x n, which describes the impurity distribution over the thickness of the spce-chrge region of the semiconductor. Copyright to IJARSET www.ijrset.com 58
ISSN: 35-38 Vol. 4, Issue, December 7 It is seen from the reltion (9) tht the lrger the vlue of S, the greter the chnge in cpcitnce C under the pplied lternting voltge U. Figure shows the experimentl volt-frd (verged over 5 smples) dependences of diode of the Au-nSi type mde on the bsis of semiconductor n is the type of conductivity. The solid dependence corresponds to the clculted current-voltge chrcteristic given in Fig. for the prmeter = 8-6. Fig.. Experimentl C-U dependences for the Schottky diode: - control diodes; - diodes exposed to pressure of 6 kbr It cn be seen tht the experimentl dependence () is in good greement with the clculted dependence, which confirms the vlidity of the impurity distribution used in clculting the lw. Dependence () corresponds to the structure subjected to the ll-round compression t pressure of 6 kbr with n exposure of minutes. It cn be seen tht fter the ction of the pressure, the voltge-voltge chrcteristic (in the pplied voltge rnge.5-.5 V) shifts to the left, which grees well with the dt of []. Such shift in the chrcteristic leds to n increse in the vlue of dc / du in this region nd to n increse in the vricp sensitivity. Then, using the method of isotherml relxtion of the cpcitnce, the concentrtion nd energy spectrum of the deep centers were determined. It is estblished tht in ll Schottky brriers mde on the bsis of structures subjected to nd not subjected to pressure, chrge exchnge of the center with n ioniztion energy of Ec-.4-.3 ev with concentrtion of Nr = 3 cm-3 is observed.moreover, before the increse in the pressure, the concentrtion of the detected center chnges insignificntly. Consequently, the observed chnges in the vricp prmeters re due to decrese in the density of sttes loclized t the semiconductor-glss interfce. Figure 3 shows the frequency chrcteristics of the mnufctured vricpe, mesured in the drk t temperture of C, subjected to pressure of 4 kbr. Copyright to IJARSET www.ijrset.com 59
ISSN: 35-38 Vol. 4, Issue, December 7 Fig. 3. Frequency chrcteristics of the mnufctured vricp As cn be seen, from Figure 3, the steepness of cpcitnce chnge from voltge s the frequency increses from 44Hz to 5kHz substntilly increses nd reches mximum vlue t 5 khz. The operting voltge rnge is in the rnge from zero to 7 volts. III. CONCLUSION The dependences of the Schottky brrier cpcity on the voltge for grdient distribution of impurities in the bse region re considered. It is shown tht s the grdient increses, the steepness of the cpcitnce chnge - the vricp sensitivity increses. At the sme time, under the influence of comprehensive pressure, the sensitivity of the Schottky brrier lso increses. In this cse, the deformtion cuses rerrngement of the defective structure of the interfce between the Si-glss nd chnge in the sptil nd energy distribution of the surfce defects, which leds to n increse in the cpcitnce sensitivity to the voltge chnge. REFERENCES []. The properties of metl-insultor-semiconductor structures / under the red. Rzhnov.-Moscow.: Science, 976. []. Gurtov V.A. Solid Stte Electronics: Proc. llownce / В.А. Gurtov. - Moscow: Technosphere, 8. - 5 p. [3]. Gusev VG, GusevYu.M. Electronics nd microprocessor technology. -M.: Higher School, 4, -788p. [4]. Vendik O. V., Prnes M. A. // Components nd technologies. 7. 9. P. 64. [5]. Spiridonov AB, Litsoev SV, Petruchuk I.I. Development of MIS-vricp with chrge trnsfer in the microwve rnge // Applied Physics, 6, No. 3. [6]. Bermn L.S. Cpcitive methods for studying the prmeters of semiconductors. -L.: Science, 97, - p.4 [7]. Stroselsky V.I. Physics of semiproducting devices of microelectronics. -M.: Higher Eduction, 9. [8]. Vlsov S.I. Tolipov D.A. Pssive solid-stte devices. Tshkent: University,. [9]. Vlsov S.I. Tolipov D.A. Pssive solid-stte devices. Tshkent: University,. []. Vlsov S.I., Sprov F.A., Ismilov K.A. Semiconductor Physics, Quntum Electronics nd Optoelectronics.. Vol. 3. No. 4. P.363. []. Shchuk AA Electronics: Studies. llownce / ed. A.S. Sigov. - nd ed. - S-Pb.: BHV-Petersburg, 8. p. 75. Copyright to IJARSET www.ijrset.com 5