Method of growing single crystals germany

 

(57) Abstract:

Usage: metallurgy of semiconductors. The inventive original germanium melted, add (3-5)10-4wt.% neodymium and pulling a single crystal on a seed crystal. Increase the lifetime of minority charge carriers and reduce the time life of the main charge carriers to the lifetime of minority charge carriers in Germany.

The invention relates to the metallurgy of semiconductor materials and can be used to obtain Germany with a high lifetime of minority charge carriers (nand low life time of the main charge carriers to the lifetime of minority charge carriers (K =o/n).

The known method of increasing the lifetime of minority charge carriers and reduce the time relationship of life of the main charge carriers and the lifetime of minority charge carriers which consists in growing a single crystal germanium according to the method of floating-zone melting (see the book Glazov C. M., Zemskova Century With Physical and technical principles of doping of semiconductors, M.: Nauka, 1967, S. 331). However, germanium grown by the method of floating-zone melting, has a high energy density, l is the parameters of semiconductor devices, made on the basis of Germany produced using floating-zone melting.

The above disadvantages can be eliminated by growing germanium on the well-known Czochralski (Glazov, C. M., Zemskov C. C. Physico-chemical basis for the doping of semiconductors, M.: Nauka, 1967, S. 309). However, not high enough lifetime of minority charge carriers and large coefficients of adhesion TO 103- 104at the temperature of liquid nitrogen (77 K) in such materials to limit its scope, particularly in the manufacture of photovoltaic devices and detectors of ionizing radiation, for which the working temperature range is near 77 K.

Also known is a method of growing single crystals of Germany by the Czochralski method characterized in that for the purpose of studying opportunities Ge-doped with properties different from the properties of Ge doped commonly used admixtures, as an alloying agent in the melt is injected alloy Germany with REE (nd). However, the above method cannot get the Ge crystals with controlled electrical parameters, which is typical for crystals grown by the Czochralski method, legs is agenie in the band gap energy levels, resulting from the doping of the refractory alloy Ge-CEA, and secondly, the resulting crystals have a high heterogeneity of the resistivity along the generatrix of the ingot due to the low segregation coefficient (1 of 10-5). In addition, the material obtained in this way, due to the fact that neodymium is introduced into the single crystal in the composition of the alloy, it is present in the crystal in the form of refractory compounds neodymium-germanium (Yatsenko S. P., Fedorov E., Rare-earth elements. Interaction with p-metals. M.: Nauka, 1990, S. 173.), and therefore has no heteronomy properties, contributing to the destruction of recombination-active centers of the crystal. Thus, in this paper it is impossible to increase the lifetime of minority charge carriers and reduce the time relationship of life of the main charge carriers to the lifetime of minority charge carriers in comparison with similar units in Ge single crystals obtained by the Czochralski (Glazov, C. M., Zemskov C. C. Physico-chemical basis for the doping of semiconductors. M.: Nauka, 1967, S. 309).

The aim of the invention is to increase the lifetime of minority charge carriers and the decrease of the ratio of the lifetime of enol is achieved by in the process of growing a single crystal by the Czochralski method from a melt containing additive impurity element of the VA group of the Periodic system, in the melt is added additive impurity rare-earth element neodymium.

The essence of the invention is that due to the high efficiency of interaction introduced into the melt of neodymium with residual process impurities, increases the degree of purification of the melt, i.e., the neodymium atoms in the melt act as an internal getter. In the grown crystal has a lower concentration recombination active centers and centers of adhesion than that of the crystal grown without additives and melt neodymium, which determines for him the high lifetime of minority charge carriers and low-ratio life time of the main charge carriers to the lifetime of minority charge carriers.

The content of neodymium in the melt should not be less than 310-4wt.%, as at lower concentrations does not increase nand reduction of K. it is found Experimentally that increasing the lifetime of minority charge carriers in 35010% at T=293 K and 68010% at T=77, and the decrease of the ratio of the times is kristallov happens when introduced into the melt of neodymium in an amount of about 410-4wt.%. Further increase in the concentration of neodymium in the melt over 510-4wt.% and up to 210-2wt.% does not improve these characteristics. When the concentration of neodymium in the melt above 210-2wt.% the lower part of the crystal is not suitable for device fabrication, because it has a modular structure. Based on the objectives to maximize the purity of the crystal and save the materials used, the weight range of the content of neodymium in the melt should be chosen in the range (3-5)10-4wt.%.

P R I m e R 1. In the "Subject 10 in the melt Germany weighing 0.5 kg injected 6,6510-6g orthophosphate neodymium as an alloying agent, providing doping Germany phosphorus. Cultivation produced by the Czochralski method in a vacuum of 10-5ATM. with a rate of 0.9 mm/min Crucible rotates with a speed of 7 rpm, and a seed crystal 20 rpm From a single crystal were fabricated samples sizes HH mm Measurement of electrical and recombination parameters showed that samples have e-type conductivity with a specific resistance =10 Ohms see the Value of nhad the value 6 410-5since at T=293 K and 2,4210-7since at T=77 K, and the ratioo/nthe value 1,410who in example 1, but from a melt containing 0.5 kg of Germany, 6,6510-6g orthophosphate neodymium, as alloying additives, and optionally 1,710-3g of neodymium, which is 3,410-4wt.4%, were produced by the same measurement as in example 1. We obtained the following values: a =10 Ohm cm;n= 2,3910-4since at T=293 K and 1,6510-6since at T=77 K;o/n=7,4101at T=77 K.

P R I m e R 3. On the single crystal germanium obtained by the method similar to example 1, but from a melt containing 0.5 kg of Germany, 6,6510-6g orthophosphate neodymium, as alloying additives, and optionally 1,0610-2g of neodymium, which is 2,110-3wt.%, were made the same measurements as in example 1. We obtained the following values: a =10 Ohm cm;n=2,1510-4since at T=293 K and 1,1110-6since at T=77 K;o/n=9.8101at T=77 K.

P R I m e R 4. On the single crystal germanium obtained by the method similar to example 1, but from a melt containing 0.5 kg of Germany, 6,6510-6g orthophosphate neodymium, as alloying additives, and optionally 510-4g of neodymium, which is 110-4wt.%, were made the same measurements as in example 1. We obtained the following values: a =10 Ohm cm;n= 7,510-5with single crystal germanium way similarly to example 1, but from a melt containing 0.5 kg of Germany, 6,6510-6g orthophosphate neodymium, as a dopant, and an additional 110-1g of neodymium, which is 210-2wt.%, the lower third of the crystal had a large structure.

As can be seen from example 2, the application of the proposed method, which consists in introducing into the melt neodymium, allows in Germany, grown by the Czochralski method, to increase the lifetime of minority charge carriers and reduce the time life of the main charge carriers to the lifetime of minority charge carriers in comparison with the prototype (example 1), which is the base object. Example 3 shows that increasing the concentration of neodymium in the melt up to 210-3wt.% does not lead to further increase of the lifetime of minority charge carriers. Therefore, based on task to maximize the lifetime of minority charge carriers and reduce the coefficient of adhesion in Germany, and also in order to conserve rare earth element, the optimal weight range of the content of neodymium in the melt is selected in the range (3-5)10-4wt.%. The proposed method allows to obtain a material for Ashotovich high value of the lifetime of minority charge carriers and low-ratio life time of the main charge carriers to the lifetime of minority charge carriers determining influence on improving the operational parameters of the devices.

A METHOD of GROWING single CRYSTALS of GERMANY, including the melting of the source Germany, the introduction into the melt additive containing neodymium, and pulling the single crystal on a seed crystal, wherein, to increase the lifetime of minority charge carriers and reduce the time relationship of life of the main charge carriers to the lifetime of minority charge carriers in single crystals of germanium, neodymium is added to the melt in the amount of (3 - 5) 10-4wt.%.

 

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3 dwg, 1 tbl

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SUBSTANCE: this process comprises growing of germanium crystals from the melt containing the main alloying admixture, stibium, and two extra admixtures, silicon and tellurium, added to the melt in amounts to their concentration therein of 0.5·1020-1.2·1020 cm-3 and 1·1019-5·1019 cm-3, respectively.

EFFECT: higher thermal stability of optical properties.

1 tbl

FIELD: metallurgy.

SUBSTANCE: claimed device comprises crucible 2 arranged in growing chamber 1 with adjacent heater 4 and heat insulator 5, seed holder 3 and thermal hollow above-crucible cylindrical shield 6. The latter is made of low-heat-conductivity material (quartz) fitted at crucible 2 from above to allow its lower part to be immersed in the melt. Said lower part has through cutouts. Note here that each of lower edges of said cutouts represents a line shaped to Archimedean arc or logarithmic spiral.

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FIELD: physics.

SUBSTANCE: when drawing, linear displacement of the crystal is carried out at a rate of 0.6-0.9 mm/min in cycles, wherein monocrystals are drawn from a melt upwards, followed by lowering the monocrystal into the melt. The ratio of linear displacement upwards and downwards is 2:1. The value of absolute displacement upwards h in one cycle is calculated using a mathematical formula of the ratio of the crucible diameter to the crystal diameter, in mm: h is less than or equal to 1.5Dcrucible/Dcrystal.

EFFECT: method enables to obtain germanium crystals with a low dislocation density.

4 ex

FIELD: chemistry.

SUBSTANCE: before beginning growth process germanium melt is kept in crucible at temperature of melting for 1-2 h. After that, growing germanium monocrystals in crystallographic directions [111] or [100] is realised with overcooling at crystallisation front within 0.5-1.0K, rate of radial growth not higher than 0.5 mm/min and temperature gradient at crystallisation front within 3.0-10.0 K/cm.

EFFECT: invention makes it possible to obtain germanium monocrystals with minimal scattering of received infrared radiation not more than 1,0-2,0 percent of received signal power.

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