INFLUENCE OF GADOLINIUM TO PROPERTIES OF

STRUCTURES OF METAL-GLASS-SEMICONDUCTOR

Bobokhujaev К.U., Nazyrov D.E., Vlasov S.I.

Kuchkarov B.H.

National University of Uzbekistan, Tashkent

dnazirov2004@mail.ru

The purpose given work is a study of the influence gadolinium on the generation-recombination performances features of the structures metal-glass semiconductor. The doping by gadolinium was carried out by a diffusive at 1200⁰С within 5 clocks from raising dusting on a surface of silicon SEP-15 of metal gadolinium. For fabrication of the test structures was used glass of the type Pb0-SiO₂-B203-Al₂0₃-Ta₂0₅ (Pb0-52%, SiO₂-29%, B₂0₃-12%, Al₂0₃-6% Ta₂0₅-1%), inflicted on surface silicon (SEP-15 with crystallography orientation <111>) from powder, with the following heating (T=680⁰C) As main method of the study was used method of high -frequency C-V features [1] and relaxation under constant temperature of capacities of the structures metal-glass semiconductor, in process of the increasing the charge of inversion layer [2].

It is discovered, that high-frequency (150 kHz) the volt-farad performances of structures with an impurity of gadolinium are displaced in field of negative voltages in comparison with control structures. Such behaviour of the С-V features to point to forming the additional positive charge on border of the section semiconductor insulator [3].

The distribution of the density of the surface states over the bandgap of silicon for control (1) structures and for structures with admixture of gadolinium (2) is shown on figure 1. It was used on 5 structures in each event. From brought figure is seen that in structure with admixture gadolinium density of the surface conditions more. In all structures with gadolinium the local maximum of density of surface states in around of energy E_С-0,35 eV is watched. According to commonly accepted notions, the formation of maxima in spectrum of density of surface states is related to impurity centers localized in the space charge region of the semiconductor. Presence defect centre in approach borders of the section semiconductor-glass must bring about increase the velocities to surface heat generation of the carriers of the charge. On figure 2 are shown temporary dependencies of relaxations of capacities control (1) structure and structure with admixture gadolinium (2). Broughted dependencies were measured at a frequency of 150 kHz and temperature -12 ⁰C, after switching the voltage from 12 to 16 volts. From brought figure is seen that velocity relaxations of capacities for structures with admixture gadolinium more than for control structures.

Fig.1. The distribution of the density of the surface states over the bandgap of silicon for control (1) structures and for structures with admixture of gadolinium (2).

Fig. 2. Temporary dependencies of relaxations of capacities control (1) structure and structure with admixture gadolinium (2).

Based on above results, it possible do following conclusion. Modification on spectrum of density of surface states in structures with impurity of gadolinium is caused by localized of electrically active impurity centers in the semiconductor near to the silicon-glass interface.

References

[1]. L.S. Berman and A.A. Lebedev. Deep-level transient spectroscopy of semiconductors. Nauka. Leningrad. 1981. [2]. M.Zerbst. Z. Angew. Phys. V.22, P.3039, 1966. [3]. S. Sze. Physics of semiconductor devices. Wiley, New York. 1984.