INVESTIGATION OF THE WIDTH OF THE FORBIDDEN ZONEHEAVILY DOPED SEMICONDUCTORS

Аннотация

INTRODUCTION of these coordinates is referred to as the impurity In heavily doped semiconductors, the interaction concentration). Due to random distribution, the of charge carriers with impurity atoms plays a impurity concentration in different parts of the special role. The absorption of light with a sample is different. When performing a frequency lower than the threshold is naturally measurement, averaging is performed over the associated with the presence of a tail of the density configurations [1,2]. of states (DS) in the forbidden zone. The total concentration of levels on the tails varies from With weak doping, an electron interacts with one substance to substance and from sample to sample impurity atom. The interaction energy is the same and is often quite large, up to 1019-1020 cm-3. for all electrons. With strong doping, the potential energy of an electron depends on the positions of Values of the light absorption coefficient at several impurities at once. The energies of the h Eg depends on the doping level. Here, carriers become random quantities. With a further mainly the deepest levels on the hosts of the increase in the impurity concentration, the overlap density of states of the PS value can participate of the wave functions of electrons localized on () at  Eg/hmay be small. The values of different impurity atoms becomes noticeable and the absorption coefficient observed the impurity level is smeared into a zone. This experimentally are the result of some averaging effect is referred to as quantum level broadening. over the coordinates of the impurity atoms (the set [3]. These broadenings of discrete levels lead to a https://www.theamericanjournals.com/index.php/tajiir 10 THE USA JOURNALS THE AMERICAN JOURNAL OF INTERDISCIPLINARY INNOVATIONS AND RESEARCH (ISSN- 2642-7478) VOLUME 06 ISSUE11 decrease in the widthforbidden zones(ЗЗ). temperature dependence of discrete energy levels in the forbidden zone of silicon was analyzed. The METHODS ( ) function GN E ,E ,T determines the presence In progress [4] a mathematical model of the 0 i spectrum of the density of surface states was of an energy level.The model has been improved constructed by expanding it into a series in [5, 6] for the analysis of the spectrum of the PS in a ( ) ( ) wide energy range. Let us consider this model for GN E ,E ,T functions. Where GN E ,E ,T is 0 i 0 i this problem. Let us decompose the spectrum of the derivative with respect to energy of the ( ) the density of energy states, Ns E ,T By probability of ionization of electrons from an 0 ( ) energy level. With the help of which, the GN E ,E ,T according to the model in the form: 0 i N (E)= N (E)+N (E)+N (E) (1) s sn ss sp n n N ( E,Т ) =for sNalaryE:N−E ( EG,NТ () E=,E,NT ) EE −E GN ( E ,E,T ) E at E  E (2) sn n0 i sn c i n0 i c i c i=1 i=1 n n N ( E,Т ) =for VNZ:NE ( −E,EТG ) =N( EN,E,T ) EE−E GN ( E ,E,T ) Eat E  E (3) sp p0 spp i i p0 p i i v i=1 i=1 n N ( E,Т ) =for thNe f(oErb)iGddNe ( nE z,oEn,eT: ) ss ssi i i i=1 n N ( E,Т ) =N (E )GN ( E ,E,T ) at E  E  E (4) ss ssi i i c v i=1 1  1  1  Where GN ( E 0 ,E i ,T ) = kT exp   kT ( E i −E 0 ) −exp kT ( E i −E 0 )      (5) boundary for photon energy from 1.2 eV to 0.6 eV. E1-can run across the entire valence, forbidden band (BG) and conduction band (CB). Ns -the Consequently, doping with impurities at deep i concentration of energy states corresponding to levels expands the band gap and the valence band. energy E , E - energy of states, T-temperature. k This enhances the absorption of light below the red i 0 - Boltzmann constant. boundary. The increase in absorption in the Experiment frequency range below the red boundary indicates In progress [7] absorption of monochromatic light a decrease in the width of the band gap. However, is observed at frequencies below the threshold. the absorption coefficient in the range of 0.6 eV-0.9 Heavy doping of silicon decreased the red eV is approximately α~1-10 cm-1 and is 3-4 orders https://www.theamericanjournals.com/index.php/tajiir 11 THE USA JOURNALS THE AMERICAN JOURNAL OF INTERDISCIPLINARY INNOVATIONS AND RESEARCH (ISSN- 2642-7478) VOLUME 06 ISSUE11 of magnitude smaller than in the region of intrinsic the energy PSs is obtained in Fig. 1.c. Using the absorption of pure silicon. As can be seen from Fig. above model (1), we will construct the PS spectrum 5.2, ( hEg ) / ( hEg ) 104 If we assume for doped silicon taking into account the experimental conditions, T=300 K, Eg=1.21 eV. It is that the absorption coefficients are proportional to evident from the figure that a high concentration of the PS (combined PS), then the PS in the former impurities gives a sufficiently large number of forbidden zone is 104 orders of magnitude lower levels determined by clusters formed by impurity than the PS of the ZP and VZ (1022-1020). levels. The levels in the forbidden zone are created In the new zone in the range of values Eg<0.9 by a random distribu