DE1639048A1 - Photothyristor - Google Patents

Description

Photothyristor

(The priority of the corresponding US application Serial No. 585 683 of 10.10.1966 is claimed)

The invention relates to a photothyristor with a semiconductor body with four layers of alternately opposite conduction types, the outer layers of which are fleas-like Connection bodies are provided.

It is well known that controlled semiconductor components or thyristors must be used can be switched to the conductive state by a control signal. Usually the control signal consists of an electrical one

Documents (ATt-VIt ^ ₂ UMS-U ₃ O..Anderuno ^ v-Ä.9.

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Impulse that occurs between the grid and the one serving as the cathode Emitter of the semiconductor component is brought to act. This requires an immediate electrical connection to the Grid. Such an arrangement has multiple nights, it may also be sufficient for some applications. In particular the conventional technique of using control lines to fire the thyristors then has various problems when a number of thyristors connected in series to high AC voltages rectify ocer for other purposes. In row switched thyristors of this type are between earth potentials and a negative high voltage potential, while the control circuit for each thyristor it is usually located between the filter and the cathode. Should, for example, a Säuie νυη thyristors a potential of 5υ.υυυ volts between earth and high voltage pol have, so is the grid of the thyristor, which is in the immediate Near the negative pole of the sow, at one Potential of approximately 5U.UUU volts to earth. This brings difficult Isoiationsprobieme with it, especially with regard to the capacitive coupling between the control circuit and the Erdpo-L.

Other difficult problems with series thyristors to a Säuie m the additional sound reinforcement Thyristors, which must extend over the entire Säuie. Em electrical control signal which is applied to a plurality of in Series connected thyristors is entered, will not be total Put thyristors in the conductive state at the same time because of the differences between the individual thyristors and their members of staff. That means that im. -Iereicn of Microseconds a thyristor blows before the others or

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at least partially ignited, so that without special wiring measures 3ich distribute the full voltage over the blocked thyristors and thus the breakover voltage of one or more of the blocked thyristors could be exceeded, with the result that one thyristor is destroyed, which in a chain reaction to the destruction of others Thyristors can lead. Usually the viewing members consist of sets of resistors and capacitors, each set bridging one of the thyristors in the column. The resistors serve to distribute a DC voltage evenly over the entire column, while the capacitances are required to distribute variable voltages i evenly. As soon as a thyristor in the column ignites, the capacitance drives a very considerable current in the rectifier, so that the current rise is in the order of magnitude of 200 A / µsec. Such a high current rise (di / dt) can lead to the destruction of the thyristors if a large inductance is not added to each element in order to limit the level of the current rise. This increases the costs for such an arrangement quite considerably.

Furthermore, conventional thyristors, which are controlled by electrical signals, are particularly suitable for such a wide range of applications not suitable where the thyristor has to switch high peak currents in a very short time. The thyristor conductivity is generated by charge carriers that flood the area between the anode and cathode contacts. When switching of the thyristor, this flooding is partly due to the ^ Teucrkontakt excited at one of the emitter junctions. The end positive and negative charge carriers existing plasma is "'

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initially between the anode and the cathode only in the vicinity of the intermediate layer between the grid and the cathode terminal. As soon as the anode-cathode current flows, it expands the plasma spreads out until it fills the entire volume between anode and cathode. The plasma takes about a period of time 4U / usk until equilibrium is reached. Soiien, for example Control pulses of 1 / µsec are generated, the 4uyusek time constant of the piasm can no longer be neglected

The outward sign of this slow plasma spread is a voltage drop that is considerably higher than that of a total cut thyristor. As the plasma spreads and almost fills the entire volume of the arrangement the voltage drop back to its normal level. The problem this effect is twofold:

First, the large voltage drop reduces the proportion of usable energy in the load resistance and, secondly, causes the resulting large heat generation within the Thyristor a local heating that adversely affects the operation of the circuit or even the failure of the component can cause.

The object of the present invention is to provide a photo thyristor which overcomes the difficulties mentioned above . In particular, when photothyristors are connected in series to form a column, balancing of the thyristors should no longer be required. '■

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This task is performed in the case of a photothyristor with a semiconductor body with four layers of alternately opposite Line type, the outer layers of which have flat connection bodies are provided, achieved in that, according to the invention, the sum ignition of the thyristor required radiant energy ge ^ -en the one outer layer is directed and that the radiant energy has such a wavelength that at least a part uavcn penetrates this outer layer and forms electron-hole pairs generated in at least one of the two inner layers.

Light-controlled thyristors are known per se. It was found io.1 a photon when it is applied to a semiconductor body e3, absorbed in the generation of hole-electron pair can ground v /. This depends on the wavelength of the light. When the pairs of holes and electrons are grounded by optical absorption, a photootrosis flows in a forward-polarized thyristor. As soon as this photocurrent is sufficiently high, the arrangement goes into the conductive state.

In older methods of optically igniting thyristors, light was radiated onto the hand of the semiconductor body or onto areas in which the pn junctions reached the surface of the semiconductor arrangement. It must be taken into account here that the semiconductor wafer is extremely thin - a practically implemented controlled silicon component is, for example, about a hundred times as wide as it is thick. From this it follows that "edge-driven ¹¹ thyristors keep vic-le -er upper parts having thyristors controlled by an electrical signal. In particular, it takes considerable time for them to blow through.

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In contrast to this, in the present invention, the radiation is on the flat surface of the one outer layer of the Directed photothyristor. This radiation has such a wavelength and intensity that it forms the first outer layer penetrates into the adjacent inner layer and to a lesser extent also into the following inner layer, in which it creates electron-hole pairs, thereby creating the photothyristor is terminated. Thus, in contrast to the older components ments a comparatively large area in the central area of the thyristor irradiated by the light and · thus in the conductive State transferred, which reduces the switch-on time and thus also improves the di / dt behavior.

As already mentioned, the .wavelength is the. Radiation so too dimensioned so that at least a sufficient part penetrates through the irradiated outer layer into the two inner layers. Wavelengths that are shorter than the intended ones generate useless pairs of slectron holes in the irradiated outer layer. Lengths of wool that are longer than the intended penetrate dc-n entire semiconductor body. If the semiconductor body consists of silicon and the irradiated outer layer is about as usual 0.01 mm thick, the best wavelength is about 93) 00 Å, i.e. it is in the infrared range and thus above the visible area. Shorter wavelengths in the visible range were largely ineffective for igniting the arrangement so that the photothyristor according to the invention does not respond to light pulses from ordinary daylight · The radiation with a wavelength of 93ÜO Sl is preferably through a gallium

Arsenide luminescent diode generates its radiation from the Diode on the surface of the irradiated outer layer of the photothyriator by means of a light guide or the like. is introduced. However, any other radiation sources can also be used if they have the required wavelength.

Further details and advantages of the invention are illustrated in exemplary embodiments explained in more detail with reference to the drawing.

Pig. 1 shows in cross section a known photothyristor, the is controlled by means of radiation acting on the edge of the photothyristor.

F-g. 2 shows a cross section through a photothyristor according to FIG the invention.

Pig. 3 shows a diagram of the conversion efficiency as a function of "the wavelength of the incident radiation.

Lie Pig. 4A and 4B show the course of the inrush current of the Photothyristor according to the invention among various Conditions. .

Pig. Figure 5 shows an arrangement for directing radiation to a variety of photothyristors connected in series and ignite them together.

Pig. Figure 6 shows details of the Pig light guide. 5, which allows a pulse of radiation from a common Source of acting simultaneously and uniformly on a plurality of photothyristors connected in series.

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In Pig. 1 shows a known photothyristor with a disk made of semiconductor material 10, which is composed of p- or n-conductive outer layers 12 and 18 and n- or p-conductive inner layers 14 and 16. The disk 10 is comparatively thin, ie its thickness is approximately 2 mm. Electrical contacts 20 and 22 cover essentially the entire flat surface of the two outer layers. The one known in Pig. 1, a light beam 24 is provided which is directed against the narrow side of the semiconductor wafer 10. As already mentioned, if a photon is directed towards the semiconductor body, it can penetrate it or be absorbed by it, with a hole-electron pair being generated. The probability of absorption strongly depends on the wavelength of the radiation. If pairs of holes and electrons are generated by optical absorption, a photocurrent flows in the photothyristor, which is poised in the forward direction. If this pr.oxc current is sufficiently high, the arrangement is switched to the conductive state. Visible radiation, which is usually used to create the hole-electron pairs, will create these pairs in close proximity to the surface of the photo thyristor. In general, electron-hole pairs that are generated in the vicinity of the surface of the photo thyristor are useless, recombinations take place on the surface, and the pn junctions on the surface have unfavorable properties. It follows that an "edge gated" photothyristor such as that described in Pig. 1 shows a poor efficiency hct because it requires considerable radiant energy to ignite. Since initially only small areas for electricity

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leadership are available, its current capacity is limited. The initially desired area is of the order of magnitude equal to the product of the diameter of the light point and the penetration depth of light.

Even for the most favorable wavelengths of visible light, the depth of the ringing is in the order of magnitude of only about 1, 1 mm. Consequently, a light spot with a diameter of .2 cm results in an elongated conductive surface on the order of 2. 10 cm This initially conductive surface is shown hatched in FIG. 1 and is designated by the number 26. The surface 26 represents a very narrow part of the entire disk 10. Assuming that favorable conditions exist and that the initially conductive surface is in the order of magnitude of 2. 1ü cm, a photothyristor that carries a current of * 0 A needs an initial current density of 5 · 10 A / cm L) ^ eS is a limit value which, if exceeded, destroys the arrangement due to overheating. The limit value a "range-controlled" photothyristor, as shown in Fig. 1, is thus about Iu A.

The light controlled photothyristor according to the present invention is shown in FIG. He also set himself from one p-conductive outer layer 12, an η-conductive inner layer 14, a p-type inner layer 16 and an η-type outer layer 18 together. The arrangement according to FIG. 2 also has two connection bodies 28 and 23, which are not graphically connected to one power source shown are connected. In the special

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Embodiment according to Fig. 2 is the lower connection body 28, which is preferably made of copper or another material of high electrical Conductivity exists, designed as a flat disk 50, with the one outer layer 12 of the semiconductor body 10 ver-Dundc.i is. The flat disk 50 continues downward in a joint 52, to which a heat dissipation body or agl. Can be consolidated.

The upper connector body 35 is an elongated shaft car, which is also made of copper or another material of high electrical conductivity. The shaft expands down to a flange 34, soft on the upper flat side aor disc 10 rests and with the outer layer 18 of this Disc 10 is connected. A cup-shaped, insulator 36 from Ceramic closes together with the connecting bodies 28 and 33 Washer 10 hermetically.

The arrangement described so far is very similar in structure to a conventional thyristor, if one disregards the fact that there is no line for the control electrode. In a further development of the present invention, a bore 38 is provided in the upper connection body ^ 3. A light guide 40 is passed through the upper end of the bore 8, one end of which preferably rests on the surface of the outer layer 18. In the vicinity of the other end of the light conductor 40, a radiation source, i.e. in the present case a gallium arsenide luminescence diode or a luminescence diode column 42, is attached. The light generated by the luminescent diode 42 is transmitted through the light guide

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brought directly to a non-metalized point on the surface of the / uüens'chicht 1S. A comparatively large area is thus acted upon by all radiation and the photothyristor is thus ignited. This is shown schematically by the arrows 44. The radiation penetrates the outer layer 18 and reaches the p-leixende Innenscnicht 16 and in a certain U; .. catches in the η-conductive inner layer 14 · The produced in the ni.itcTiden AuLsenschicht 18 Eiektronen-hole pairs weraen ■ χ :: , essentially destroyed by recombination. On the other hand, most of the electron-hole pairs that are generated in the ε-layers 14 and 16 serve to ignite the photothyristor "with the help of a photocurrent. In a multilayer structure, however, the photocurrent is also increased equal to the product of the photocurrent, which would flow in the presence of only one pn junction, with the current amplification factor of the entire pnpn arrangement, which is calculated analogously to the emitter circuit current amplification factor of transistors.

In Pig. 3 is a graphical representation of the "diode" effect * gray E of an arrangement according to the present invention as a function of the wavelength or the photon energy. It can be seen that the efficiency is highest when the length of the incident radiation is in the range of about 8uüu - lUüüO $. is located. Below 800υ k, ie in the range of visible light, the degree of efficiency decreases very sharply. The photocurrent flowing in the arrangement results from the efficiency E χ the current amplification factor ρ χ dem

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"Lichi ^ -Strom. Under the term" Lichf-Strom is the number of photons to understand, aie per second on the arrangement occurs, multiplied by the charge of an electron.

Dcrauj results in:

P'.jtCotrom = E χ (i χ "Lichf'-current. If one considers these factors as a whole, including the reflection on the surface of the outer layer 18, it follows from this that an approximate equality between"Lichf'-Stroa and the Since one needs about 1UU mA for the reliable ignition of a thyristor, a "light" current of about 1UU niA is required.

Since the irradiated outer layer 18 is about 1/2 mm thick, the most favorable wavelength is about 90 ° p. 24 With visible light the arrangement would have a very poor efficiency, which can be clearly seen from the graph on the curve in Pig. t> results, aie shows how the efficiency drops very sharply in the area of visible light. Shorter wavelengths would only produce useless electron-hole pairs in the irradiated outer surface 13. As the time allotted Galiium-Arsenia luminescence dioce 42 sends its entire radiant energy in a narrow Bandoreite near 85U0 S., she is a vorzüg- "Liehe radiation source to ignite the photothyristor.

2c, tests were carried out on photothyristors according to the invention with a gallium arsenide diode as the pulse radiation source. The radiation was

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Light guide like he did in Pig. 2 is denoted by 40, au ι 'die Surface of the Siiisiumscheibe 10 brought. The resulting Waveform of the anode current in the event that the photothyristor öaau was used, a capacity iicc-r a 10.-..- large Discharge resistance is in the pig. 4A and 4B. The course of the anaenous current is dependent on the Zv.it shown. The waveforms 44 and 46 in Pig. 4A receives E1L..1 rr.with a comparatively low radiation intensity in The order of magnitude of 50 mA "light" current.

1. It should be noted that the diode current resulting from the radiation _ .. pu..3 on the irradiated outer layer has two areas that are clearly distinguishable from one another. At first the current is only small, on the order of 60 mA. The current peaks of about 60 mA are obtained after about 0.5 / µsec, calculated from the effect of the radiation pulse on the irradiated outer layer. This is essentially simply L..U the amplified photocurrents. The lower curve 46 in Pig. 4A, b-'i the current drops to the value ..Hull, is due to the fact that the radiation intensity was too low to turn on the photo thyristor. The upper curve, on the other hand, is obtained under the condition that the photothyristor is ignited due to the radiation pulse. During the first 2.5 / µsec, the anode current represented by waveform 44 is about the same as that represented by waveform 46, with the photothyristor not firing. From a point in time about; yusek onwards, the conditions for the ignition of the thyristor are established and the anode current rises sharply.

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The time between the effect of the cathode pulse (time "KuIl" in Pig. 4A and 4B) and a time at which the Switch-on conditions are met and the current increases sharply, is called the hold-on delay time. In the case of the ■ Waveform 44 in Pig. For example, in Fig. 4A, the turn-on delay time is approximately 3 / µsec, which is quite long.

Dio in Pig. The waveform shown in FIG. 4B shows the behavior at already large current of the thyristor according to the invention. This resulted in a higher radiation intensity in the order of magnitude of about 5 A "Lichf 'current is used. The resulting Switch-on delay time. in Figure 4B is about 0.7 / µsec when compared with the 2 / µsec for waveform 44 in Figure 4A. In Pig. 4B the thyristor ignites completely within Ü.8 / usec. At this point the current is hardly through the thyristor itself, but determined by the external conditions of the circle. In this case the peak current is about 25 A and the rise time of the current is less than 0.1 / µsec. This switch-on time of 0.1 / µsec is, as mentioned, much shorter than it is with conventional ones Thyristors can be achieved. This can be explained as follows:

When switching on, the rise time of the current is generally determined by the ratio L / R in the conductor loop including the ^ cos thyristor. If the external loop inductance L is kept low compared to the resistance R, the rise time is still limited by the inductance of the switch. The current in conventional thyristors is initially

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guided in thin stroia threads, which because of their small thickness represent effective inductance. In the photothyristor according to the present invention, a large area is covered from the start ignited, which results in a low effective self-inductance. In the fully ignited state, the current drops exponentially a time constant which is determined by the value of the capacitance acting as an energy source and the charge resistance.

The values for the rise in electricity (di / dt) can be taken from the Pig. 4-B can be read. The maximum value of the current rise under these conditions was estimated to be about 400 A / usec. Comparative Analyzes between a conventional thyristor and the thyristor according to the invention show that in the present invention the di / dt behavior of the thyristor by at least an order of magnitude improved: is.

? ig. 5 shows an arrangement for igniting series-connected thyristors. The thyristor ©;?. siM denoted by ä @ n reference _{symbols T 1} , T ₂ , Τ-, etc. The thyristors are connected in series with a load. The load is a schematically shown resistor 48 which is located between the * · Srdpotentiai and the point 50 with a high negative potential. It should be noted that no compensation circuit is provided parallel to the thyristors, because the switch-on time of all thyristors is extremely short and the thyristors are practically all switched on at the same time.

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A gallium arsenic Lummeszens diode array 52 is in one Cooling liquid submerged, for example liquid nitrogen, in a container 54 · In some cases, a cooling medium be waived at all. For example, the diode array 52 may contain a variety of individual diaphragm layers, which is directly applied with the help of a thin layer of solder in a pn-

pr. pn series with heavy Kolybdenum electrodes at the ends

connected and in a common chamber for all Ι-οαοΛ the sows are housed. Pulses of electrical energy from about 10U to 20U A for aie diode array 52 is obtained from a pulse generating network 56 associated with assembly 52 is connected via a supply line 58. The gallium arsenide luminescent diode array 52 is directly connected to a light guide system, which consists of a main light guide 60 of large diameter, which at one end m a Variety of light guides 62, 64 and 66 with smaller diameter is divided, which in turn through the bores 58 (Pig. 2) su each one of the thyristors T- to T- * are performed. Since the Radiation is sent from a common source, viz the allium arsenide luminescent diode assembly 52 the light pulses simultaneously on the thyristors T .. to T on.

"Yes, but completely identical switch-on characteristics of the in To obtain series connected thyristors, the amplitude must be achieved of the light pulses that are fed to the individual thyristors must be the same. A system to the pulse of light to be divided evenly among the thyristors, m Fig. 6 car posed. The large diameter light guide 60 is shown in FIG

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parts A and B divided. Part A consists of random fiber lines 68, arising at the input together and separated at the output end and thus light guides 62, 64 and 66 with a small diameter, which are guided to the corresponding thyristors T to T. ₅ The entrance or surface 70 of part A is polished flat. Part B comprises a short stump of solid light guide. Its ends are polished and have smooth and parallel surfaces, one of which is bonded to surface 70 of part A with an optically matching adhesive The radiant, polished surface of the light-emitting diode is directed towards the polished surface 72 of part B. Although only a single diode is shown in Figure, several diodes 52 can also be connected to the surface 72. In this case, all diodes transmit simultaneously their radiation off.

Part A has randomly distributed fibers, despite uneven irradiation at the entrance uniform light to the Send out exit. The problem, however, is that in the event that the irradiation is not uniform, because of the limited resolution of the fiber bundles, namely the finite one

Fiber diameter, only a few fibers that open into the exit bundles 62 to 66 really emit. This is of course an undesirable situation and would lead to uneven light output & outG for the individual thyristors · Although the combined output of the light guides or bundles 62 to 66 may be the same , * o the thyristor is more likely in patches of the size

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of the individual fibers in each bundle as being uniform across its Illuminated control surface. Ais control surface is the area of the irradiated Auflenschicht to understand the under the bore 38 in Fig. 2 by a plurality of small light spots instead a single large light spot is illuminated. It is possible that this patchy lighting of the control surface some Advantages in terms of speed and di / dt behavior could cancel * Bas is the light emitting area of the diode a line about 0.05 cm long and less than ϋ, υΟΙ cm Expanse. In the plane perpendicular to this line source, the radiation scatters according to the laws of refraction. The total angle this spread is on the order of about 10 °. The stub II B in Fig. 6 makes use of this diffraction by refraction in two ways:

First, the radiation source is set back from the surface of the actual entrance 70 to be relatively uniform To achieve illumination of the entrance. You will make the stub B so that by its cross-section and its length defined solid angle is approximately equal to the solid angle of the radiation from the line source. The second purpose of Mute B is to serve as a light guide by partially capturing the light emitted at particularly large angles.

The input end of the light guide is mechanically attached to the electrical pulse transmission line and immersed in the cooling liquid.

If the number of thyristors connected in legs grows, must also the number of gallium arsenide diodes, which are 72

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in Pig. 6 are attached, can be increased. The common gallium arsenide luminescent diode works at 77 ° K and emits peak "light" pulse currents of 10 A at a frequency of 2UO pulses / sec. The individual gallium arsenide luminescent diodes 52 are of such a size that about 10 of them are attached to the plate 72 in Pig. 6 can be attached. This gives a total "light" current of 100 A. Taking into account the absorption and reflections in the light guides, rr.cn can assume that about 30 ^ of the emitted radiation reaches the thyristors. This gives a "light" flow of approximately 30 L ·. Since, as mentioned above, about 100 mA of λ "light" current is required to ignite a thyristor, more than 100 thyristors can be connected in series under the specified circumstances.

The kit of the present invention becomes a high current and high voltage silicon photothyristor created with two electrical connections, which is characterized in particular by that the di / dt ratio is an order of magnitude better than at the conventional thyristors. In addition, it can be switched faster than the known thyristors. Moreover, simplified the ignition by radiation the electrical isolation of the grids from the control source. In addition, a'-undesirable Ignition of the thyristor by scattering electrical signals or light signals, for example by medium light, is prevented.

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Claims (1)

PLA 67/8250 ίο Claims . 1. Photothyristor with a semiconductor body with four layers vcfl. alternately opposite conduction type, its outer Layers are provided with planar connection bodies, characterized in that the one required for triggering the thyristor Radiant energy against the one outer layer (1S) is directed and that the radiant energy has such a wavelength that at least a part of it this outer layer (18) penetrates and electron-hole pairs generated in at least one of the two inner layers (14 ·, 16). 2. Photothyristor according to claim 1, characterized in that the Semiconductor body (10) consists of silicon and the wavelength of the radiant energy * is about 7,000-10,000 pounds. 3. Photothyristor according to claim 1 or 2, characterized in that the irradiated outer layer (18) has a thickness of about 0.01 mm and the wavelength of the radiant energy is 8500-9300 1 . 4. Photothyristor according to claim 1, characterized in that the radiant energy is brought to the irradiated outer layer (18) by means of a light guide (40), one of which is adjacent to the irradiated outer layer (18) and on the other end of which a radiation source (42) with a wavelength of about 7000 - 10 000 & acts. Ntut inferior - 20 - 00 988 A / OS 6 2 ^{H1 / Approx} £ Λ PLA 67/8250 5. photothyristor according to claim 4, characterized in that as Radiation source (42) a. Gallium arsenide luminescence mode is provided. 6. photothyristor according to claim 1, characterized in that a first planar connection body (30) on the non-irradiated Outer layer (12) and a second planar connection body (33) is attached to the irradiated outer layer (18) that the second connection body (33) essentially has the shape of a Has cylinder and that the radiant energy is brought to the irradiated outer layer (18) through a bore f (38) of the cylinder is. 7. photothyristor according to claim 6, characterized in that the bore (38) of the second connection body (33) along the Cylinder axis extends. 8. Photothyristor according to claim 1, characterized in that the intensity of the radiant energy is so great that the number of λ emitted photons per second times the charge of an electron is at least 10 mA. 9. Arrangement for introducing radiation pulses of the same intensity at different locations, preferably at different photothyristors, in particular according to claim 1, characterized in that that a first part (A) of a light guide (60) with "large diameter au3 randomly distributed fibrous - 21 - Hl / Ca 00988 ^ / 0562 BATH ORIGINAL « J PLA 67/8250 Light guides (68), which are common at the input of the radiation pulses and at the exit of the radiation pulses end in individual bundles, composed so that the bundled light guide fibers several light guides (62 ·, 64, 66) with smaller: form the diameter, which leads to the individual points to be irradiated lead that a comparatively short second part (B) of a light guide (60) 'with a large diameter parallel and flat Has surfaces, one of which is adjacent to the entrance of the first light guide part (A) and that radiation pulses the other flat surface (72) of the second light guide part (B) are fed, so that the radiation pulses the two Hike through parts (A, B) of the light guide (60) and finally to the variety of light guides (62, 64, 66) with smaller ones Diameter can be distributed. fO. Arrangement according to Claim 9 »characterized in that the radiation emitted from the exit of the many light guides (62, 64, 66) with a smaller diameter each against one of the outer layers (18) to be irradiated by series-connected photothyristors (T ₁ , T ₂ , T ₅ ) is directed. 11. The arrangement according to claim 9, characterized in that the on the other flat surface of the second part (B) of the light guide (60) with large diameter directed radiation pulses emitted by a gallium arsenide luminescent diode. - 22 - "· Hl / Ga 009884 / OS 6 J BAD τ * PLA 67/8250 12. The arrangement according to claim 9, characterized in that the The entrance side of the first part (A) of the large diameter light guide (60) has a polished and flat surface, the one with a flat surface of the second rope (B) of the light guide (60) with a large diameter with an optical adapted adhesive is connected. - 23 - Hl / Ca 00988A / 0E62 '■ ·' · ' ⁽ - BATH ORIGINAL 2 / Blank page