DE1589157A1 - Electric light bulb - Google Patents

Description

Patent attorneys Λ CQQ Λ C "7 ZELLENTIM & LUYKEN ° '

8000 Munich 22 Zwclbrödtcnstr. 6th

Hziceskij institut imeni N.J. Leebedeva March 7, 1967 AN SSSR L / Hu

Moscow / USSR _{p χ}

Electric light bulb

The invention relates to electric incandescent lamps, the luminous body of which consists of a semiconductor.

The usual electric light bulbs have a WoIf * - Ram filament as a luminous element · Since the main part of the emitted energy of a tungsten filament is not in the visible, but is in the infrared, the light yield is low. This is due to the fact that the absorbency of the tungsten depends only very little on the wavelength and that thus the radiation spectrum of the glowing tungsten according to Kirchhoff's law, that of a black body comes near.

We now know two ways to increase the light ** yield of electric light bulbs, namely the Brhöln * ng the filament temperature and the use of selective - shine #

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The first possibility is based on the fact that the maximum of the emission spectrum of a black body, similar to the Wierian law of displacement, shifts to shorter wavelengths with increasing temperature light output of a black body reached at about 700O ⁰ K to maximum value · with a further increase in temperature, the light output due to a rapid increase reduces the energy content of the ultraviolet radiation. No substance remains solid at 700O ⁰ K Even if it were possible to develop a black body for this operating temperature, the gain would not be too great, because in this ideal case only 37% of the total emitted energy would be accounted for by visible radiation. It is easy

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It is understandable that * '- if one wants to follow this path - encounters many difficulties which are connected with the instability of the luminous element at high temperatures. Up to now, incandescent lamps could only achieve a luminous element temperature of 320O ⁰ K.

The second possibility is realized in that one the luminous body from a transparent for the infrared radiation Material manufactures · According to Kirchhoff's Geseta, such a luminous element does not emit any energy in the Infrared · This means that all of the emitted radiation is in the

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s-iolitable spectral range, (partly also in the ultraviolet), The light output of an incandescent lamp with such a luminous element is very high. The only difficulty is to find a suitable material for the production of such luminous bodies 2u.

Bs are known proposals to manufacture the Leuuntkörper from a chemically pure and sufficiently heat-resistant semiconductor with a broad forbidden zone (see, for example, the magazine "Optika i Spektoskop! Ja", Volume IJ _9, page 612, 1962, Moscow). However, GU unlamps with such a luminous element have a number of disadvantages.

A stable heating process of the lamp body is very difficult to achieve, for example with such lamps. For this purpose, either uer filament must very α inn seJ.n to the infrared radiation by free electrons reduce, or Leuchtkörperte-aperatur must be very _high:: e :: - 3, ~ zen, sufficiently to maintain the temperature dependence of the electrical conductivity of the Leuchtkörpers- abzuscnv.acnen

As a pure semiconductor with a wide verboüeuer zone Room temperature has a very high contradiction. has, he can with Stromdurchr.aiig only uaiin erniest v.erde;:, / enii an AniantstemperatUi ^ is sufficiently high «Therefore, a powerful tinder is required for such incandescent lamps, the

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can heat the filament to a temperature of 1000 ⁰ K _e Hi ^ nto is that it is very difficult to produce a sufficiently large body of a chemically pure refractory semiconductor "

The invention aims to eliminate these disadvantages.

The invention is based on the object of specifying an electric incandescent lamp with a semiconductor luminous element, which has a high luminous efficacy, can be heated stably and auto-ignition of the incandescent lamp at room temperature regardless of the temperature

According to the invention, this is achieved in that the luminous element is manufactured from a semiconductor, as is the case is still alloyed with additives that even at temperatures that occur in the glowing luminous body, the Conductivity of the semiconductor is still due to imperfections is determined. Both acceptor and

17 as well as Ilonatorubstanzen in concentrations of 10 'to 10 cm * "* · Bs is however to avoid both types of Adding additives at the same time »

"The light bulb will auto-ignite, go. the ignition without external heat source, desired at room temperature, see above are such additives to be desired in which those of them generated energy levels from the conduction band (for donors)

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or of the valence band (for acceptors) not more than stand out by 0.5 eV. If auto-ignition is required at lower temperatures, admixtures can be added where this distance is even less, namely bip about 0.3 eV.

Alloyed silicon carbide is particularly suitable as the material for producing the luminous element. If nitrogen and phosphorus are used as alloy additives, the incandescent lamp will self-ignite. To the alloy further suitable aluminum and boron _e

In order to reduce energy losses through heat conduction, the piston can be double-walled in the manner of a Dewar vessel. The light output depends to a large extent on the material of the bulb. In the case of glass it is 10% and in the case of quartz it is 20% higher than that of a semiconductor incandescent lamp with a conventional bulb »

The invention is explained below with the aid of some exemplary embodiments explained in more detail with reference to the drawings

The Pig. 1, 2 and 3 show the radiation spectra of the Luminous body of a semiconductor incandescent lamp with different Temperatures

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First of all, let us consider the principle of operation of the semiconductor incandescent lamps considered which one is independent of whether the luminous element is made of a pure or alloyed semiconductor consists.

In Figs. 1, 2 and 3, the abscissa axis is the quantum energy hv and the radiation power E plotted on the ordinate axis in arbitrary units · The full The solid line shows the luminous spectrum of a semiconductor luminous body una the dashed the spectrum of a black body. In the infrared region A is the spectrum of the semiconductor luminous element by wide oblique hatching and in the visible area B by vertical hatching marked.

The diagrams clearly show that the energy emitted by the semiconductor luminous element is in the infrared is much smaller than that of a blackbody because the semiconductor in this area is transparent. The iig. 1, 2 and 3 refer to increasingly higher temperatures of the light body * "A comparison of the SG hood images shows that the energy component of the visible radiation always changes with increasing temperature, with the width of the transparency range of the semiconductor decreases, which is due to the decrease in the width of the forbidden zone is due with increasing temperature. As long as the shortwave limit of transparency G- (Fig. 1) is still in

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visible area, the power emitted in the visible spectral area increases faster with temperature, in order to increase the total power emitted. However, the power that is emitted in the ultraviolet increases much faster. However, since its absolute value ^{is small at temperatures below 3OCX) 0} K, it does not play an essential role. But if the limit of transparency shifts into the infrared range (C ₀ and C-, in Fi ;;. 2, 5), it increases the proportion of infrared radiation increases rapidly * This soon leads to a decrease in the luminous efficiency of the luminous body. Therefore, the optimum operating temperature of a luminous body made of a semiconductor is below the optimum of a black body. The maximum value of the light output of the semi-luminous body can be greater than that of the chattering body.

The radiation of a semiconductor in the area of its transparency 1st to be through according to the Kirciihorfijchen law Absorbance: s determined in this area. An increase The absorption has a decrease in light from prey Consequence · At the same time the maximum value cer decreases Luminous efficiency towards the higher temperatures. So it is favorable because of the absorption capacity in the area of visibility to keep it as small as possible. This means that the light fitting should then be designed if at all possible. '«Vie Calculations have shown, the thickness of the luminous

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body with expansion of the transparency range towards the longer wavelengths more and more · on the other hand the absorption capacity of the luminous element is also determined by the concentration and composition of the additives determined in the semiconductor · One can now prove mathematically that the depth of the energy levels, which by the Donors or acceptors were generated, from the corresponding electron band do not protrude by more than 0.5 eV should, otherwise the amount of energy emitted in the infrared will increase excessively.

The calculations also show that the maximum of the light output of the luminous element increases with the width of the The forbidden zone of the semiconductor shifts towards the higher temperatures and becomes ever narrower, the Maximum value of the light output becomes greater. However, an increase in temperature is due to the heat resistance of the semiconductor, from which the filament is made, a limit is set. For this reason, semiconductors are also excluded excessively wide forbidden zone. It has been shown that the optimal width of the forbidden zone is a half The luminous body is around 3 eV at room temperatures

such semiconductor,

The light output of a "luminous element can be very high ^{at an optimal temperature of about 250O 0 K.}

The hexagonal silicon carbide has a forbidden zone with a. Width, which is about 3 β V. Therefore it is suitable

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good for making filament ^ according to the width In the forbidden zone, aluminum nitride, toroid dioxide and titanium dioxide are also suitable.

The heating of the tungsten filament in conventional incandescent lamps by continuous current does not pose a problem. It is different It is the case with a plate made of a semiconductor, namely with increasing temperature the semiconductor resistance decreases · As a result the current flowing through the plate increases, so that also Joule's heat is developed, with which the temperature further increases, which causes a further increase in current and so on. Therefore, a current-heated semiconductor burns generally unstable

This difficulty can be avoided with semiconductor incandescent lamps As is easy to see, the semiconductor remains stable if the heat deprivation increases faster as the temperature rises as the heat development · Then there may be an increase in Joule's heat did not develop a temperature rise cause more, as this prevents the increasing heat losses This can be achieved by alloying or doping the semiconductor with additives in concentrations, which are sufficient for the semiconductor to operate at operating temperatures (which, as mentioned, are adhered to by the optical bigenso of the filament determined! be), its impurity conductivity maintains · The 'reohnungen have shown that the impurity concentration in the order of magnitude of

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... 10

10 " to 10 qhT ^ 1-should. The energy levels that are generated with the impurities should, as mentioned, not be further than about 0.5 eV from the conduction or · valence

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band protrude · Boron is a suitable additive for silicon carbide · If ignition without an extraneous heat source is required, the conductivity of the luminous element at room temperature must be sufficiently high by 0.3 eV from the corresponding bands, ignites _{at an ambient temperature of about O 1} ^{0 C.} If this distance is 0.15 eV, the incandescent lamp also ignites at -70 0 · Such energy levels can be achieved with silicon carbide by alloying with nitrogen and phosphorus ·

In the case of an electric lamp with a semiconductor filament, the energy losses due to heat conduction are around half of the total supplied energy. Hence, the reduction in conduction losses is one Reserve for a further increase in light output. One can now show mathematically that the arrangement of the filament in a double-walled flask, the space between the wall is evacuated in the manner of Dewar's vessel, reduce the energy losses through heat conduction by 20 to 40% allowed. This corresponds to an increase in the yield of 10 to 20%

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It should be mentioned that the application of such flopple-walled bulb in incandescent lamps with a tungsten filament not worthwhile, as there the increase in light output that can be achieved is low

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Claims (1)

cell; - :; ΐ .-- ί 6 luyken ₇ . _M arch 1967 8000 Munich 22 Zweibrückenstr, 6 Tj / Hu p 12707 Claims Μ ») Electric incandescent lamp with a luminous element arranged in a bulb and consisting of a semiconductor, characterized in that the semiconductor luminous element is alloyed with donor additives in consistencies of 10 'to 10 cm *"-' which in it have energy levels of not less generate than 0.5 eV below the conduction band _o 2. Electric incandescent lamp with a semiconductor filament, characterized in that the semi-conductor filament 17 is alloyed with acceptor additives in concentrations of 10 'to 10 cm " ⁵ , which generate energy levels in it of no more than 0.5 eV above the valence band. 3 · Electric incandescent lamp according to claim 1, characterized in that the semi-conductor filament is alloyed with donor additives which generate energy levels of up to 0.3 eV in it _e £ 09815/0949 Electric incandescent lamp according to Claim 2, characterized in that. indicates that the semiconductor luminous element is alloyed with acceptor additives, the energies in it! generate up to 0.5 eV © 5β electric incandescent lamp according to claim 1, characterized in that that the lamp is made of silicon carbide alloyed with nitrogen and / or phosphorus 6 · Electric incandescent lamp according to Claim 2, characterized in that the luminous element is made of an alloy alloyed with aluminum Silicon carbide is made. Electric incandescent lamp according to Claim 4, characterized in that that the filament is made of silicon carbide alloyed with boron, 8. Electric incandescent lamp according to claims 1 to 7 »thereby characterized in that the piston is double-walled in the manner of the Dewar vessels 009815/0949 Blank page