CA1113190A - Light-controllable thyristors - Google Patents
Light-controllable thyristorsInfo
- Publication number
- CA1113190A CA1113190A CA300,385A CA300385A CA1113190A CA 1113190 A CA1113190 A CA 1113190A CA 300385 A CA300385 A CA 300385A CA 1113190 A CA1113190 A CA 1113190A
- Authority
- CA
- Canada
- Prior art keywords
- zone
- thyristor
- emitter
- auxiliary
- region
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000004065 semiconductor Substances 0.000 claims abstract description 7
- 230000015572 biosynthetic process Effects 0.000 claims 1
- 206010034960 Photophobia Diseases 0.000 abstract description 2
- 208000013469 light sensitivity Diseases 0.000 abstract description 2
- 239000004020 conductor Substances 0.000 description 4
- 239000002800 charge carrier Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 1
- 230000000875 corresponding effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000012777 electrically insulating material Substances 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000000463 material Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/111—Devices sensitive to infrared, visible or ultraviolet radiation characterised by at least three potential barriers, e.g. photothyristors
- H01L31/1113—Devices sensitive to infrared, visible or ultraviolet radiation characterised by at least three potential barriers, e.g. photothyristors the device being a photothyristor
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Thyristors (AREA)
- Light Receiving Elements (AREA)
Abstract
A B S T R A C T
Disclosed is a light-controllable thyristor having a semiconductor body with cathode and anode faces, the body comprising a cathode side base zone the doping of which is reduced in a region adjacent the anode side thereof, a main emitter zone located in the base zone at the cathode face, a region at the cathode face intended to be exposed to light during operation of the thyristor, and an auxiliary emitter zone located in the base zone at the cathode face between the main emitter zone and said region. The main emitter and auxiliary emitter zones are provided with main emitter and auxiliary emitter electrodes respectively, the auxiliary emitter electrode also contacting the base zone. At least one trench is provided in the cathode face of the body extending into the base zone and having a depth at least equal to that of the auxiliary emitter zone, the trench bounding the periphery of the auxiliary emitter zone facing the main emitter zone and serving to separate a part of the auxiliary emitter electrode which contacts the auxiliary emitter zone from a part thereof which contacts the base zone.
while the base zone has a high degree of doping where required, the auxiliary thyristor has a high light sensitivity.
Disclosed is a light-controllable thyristor having a semiconductor body with cathode and anode faces, the body comprising a cathode side base zone the doping of which is reduced in a region adjacent the anode side thereof, a main emitter zone located in the base zone at the cathode face, a region at the cathode face intended to be exposed to light during operation of the thyristor, and an auxiliary emitter zone located in the base zone at the cathode face between the main emitter zone and said region. The main emitter and auxiliary emitter zones are provided with main emitter and auxiliary emitter electrodes respectively, the auxiliary emitter electrode also contacting the base zone. At least one trench is provided in the cathode face of the body extending into the base zone and having a depth at least equal to that of the auxiliary emitter zone, the trench bounding the periphery of the auxiliary emitter zone facing the main emitter zone and serving to separate a part of the auxiliary emitter electrode which contacts the auxiliary emitter zone from a part thereof which contacts the base zone.
while the base zone has a high degree of doping where required, the auxiliary thyristor has a high light sensitivity.
Description
The present invention relates to light-controllable thyristors having a semiconductor body which, at the cathode face, has at least one region which is intended to be exposed to light during operation o~ the deYice, the bcdy having at its cathode side a main emitter zone and an auxiliary emitter zone which lies between the main emitter zone and the region to be exposed to light, and a cathode base zone the doping of which falls towards the anode side of the zone, the emit es f~ zones being provided with respective electrodes, thar of the au*~liary emitter zone also contacting the base zone.
Such a thyristor is already known. It consists basically of two parts, one of which is in the form o~ a light-controllable auxiliary thyristor and the other 2 main thyristor. The light-controllable auxiliary thyr~stor serves as a control current amplifier for the main thyristor whicn carries the load current after ignition has been initiated.
If desired, a further auxiliary thyristor can be located between the light-controllable auxiliary thyristor and the ma~n thyristor.
When the surface region which is intended to be expose~ to light ~n use, is in fact illuminated, the photo-current of the light-controllable auxiliary thyristor is arranged to flow into an electrode (known as a collector electrode) which contacts this region, whence it flows in t~e radial direction to the emitter of the auxiliary thyristor and that of the main thyristor. If the emitter-base voltage exceeds a specific value, for example, 0.5 V, at a point on the p-n junction between the base zone and the .. ~.
-.
.. ' ~.
. . ' , -emitter zone of the auxiliary thyristor or of the main thyristor, the thyristor in question ignites.
In practice, it is desira~le to dri~e the light-controllable auxiliary thyristor via light conductors.
Such light conductors normally have a diameter of 1 mm or less. In order to achieve a good du/dt stability which is dependent upon, inter alia, the conductivity of the base zone, the diameter of the region intended to be exposed to light should, on the one hand, be arranged to be only just . ~ , .
sufficiently greater than the diameter of the light conductor to enable it to be contacted. In order that the least possible light power has to be used, the sensitivity of the light-controllable auxiliary thyristor should, on the one hand, be high. The light sensitivity can be increased, for example, by providing the base zone with a high specific res~stance-by means of low doping so that even with low current values, the voltage drop required for ignition is obtained.
i- It is an ob~ect of the present invention to pro~ide a thyristor of the above_mentioned type in which whilst the base zone has a high degree of doping where required, the auxiliary thyristor has a high light sensiti~ity.
According to the invention, there is provided a light-controllable thyristor having a semiconductor body with cathode and anode faces, said body compricing a ~athode-s-de :
base zone the doping of which is reduced in a region adjacent the anode side thereof, a main emitter zone located in said base zone at said cathode face, a region at said cathode face intended to be exposed to light during operation of the thyristor, and an auxiliary emitter zone located in the base zone at said cathode face between said main emitter zone and said region, said main emitter and auxiliary emi~ter zones being provided with main emitter and auxiliary emitter electrodes respectively, said auxiliary emitter electr~de also contacting said base zone; wherein at least one trench is pro~ided on ~he cathode face of said body extending into said base zone and having a depth at ^~ least equal to that of said auxiliary emitter zone, said trench bounding the periphery of said auxiliary emitter - zone facing said main emitter zone and serYing to separate a part of said auxiliary emitter electrode which contacts sa~d auxiliary emitter zone from a part thereof which contacts said base zoneO
- The invention will now be further described with reference to the drawings, in which :-~igure 1 is a schematic plan view of the cathode s~de . of a semiconductor body of a first exemplary embodiment of the invention;
Figure 2 is a section taken along the line II-II o~
Figure 1;
F~gure 3 is a section taken along the line III-I}I of Figure 1;
Figure 4 is a schematic side-sectional part of a second exemplary embodiment of the invention;
Figure S is a schematic plan view of the cathode side of a semiconductor body of a ~hird e~empl~ry embodiment o~ the invention;
y _ ' -- - - .- - - . ~ -. - .
. .' '- . -- ' '" ' ~ ~ :: ' ' ' -- . . . ~ . ~
~ ~31~
P~gure 6 $s a section taken along the line VI-VI
of Figure 5;
Figure 7 ~s a schematic plan view of the cathode side of a semiconductor body of a fourth exemplary embodiment of the invention; and Figure 8 is a section taken along the line VIII-VIII
of Figure 7.
In the various Figures, like elements (either in f~ structure or in function) ha~e been indicated by the same reference numeral. In the plan views, Figures l, 5 and 7, the electrodes ha~e been shown shaded for the sake of lmproved clarity.
The sem~conductor body shown in Figure l has a main emitter zone l, an auxiliary emitter zone 2 and a base zone lS 3 whi~h is common to the two emitter zones and the doping of which decreases with d~stance from the cathode surface of ~he ~ body. The auxiliary emitter zone 2 forms a part of a light-; ~ ~ controllable auxlliary thyristor, whilst the main emitter zone ~ forms part of a main thyristor. The main emitter zone 1~is contacted by means of an emitter electrode 5, and the~auxiliary emitt zone 2 by means of an auxiliary emitter electrode 4. The base zone 3 has a region 8 which is exposed at the surface and is intended to be exposed to light in use of the device. This region 8 is surrounded by an annular collector ~electrode g, the outer periphery of which ha a projecting portion 10 in the form of a segment of a circle.
The auxiliary emltter zone 2 in plan view is in the fonm of a segment of an annulus. That part of the auxiliary emitter S -- ~ ' :' . :
- . . : : . ~
, , .: .. :; . , . - . . --. .. ~ . . . .
electrode 4 which contacts the auxiliary emitter zone 2 is separated from that part of the auxiliary em~tter electrode 4 which contacts the base zone 3 by a trench 6, which also has the shape of a segment of an annulus, along a part of the periphery of the aux1liary emitter zone 2.
Between the region 8 o~ the surface of the base zone 3 which is intended to be exposed to light and the emitter electrode 4, there is located a further trench 7 which also has the shape o~ a segment o~ an annulus and the ends of ~0 which overlap with the respective ends of the trench 6 and of the emitter zone 2. The part of the auxiliary emittPr zone 2 carrying that part of the auxiliary emitter electrode 4 which also contacts the base zone 3 forms arms ~1 wnich are bounded on their opposite ~ides by the trenches 6 and 7.
lS The inner periphery of the trench 7 lies along the outer periphery of the part ~f the collector electrode 9 not provided with the pro~ection 10.
When the region 8 is expose~ to light, pairs of charge - carriers are produced in the base zone 3, and, w~th the indicated negati~e polarity of the emitter electrode 5, the holes f~rst flow towards the surface of the region 8 and then radi~lly outwards, whilst the electrons are dr~wn away to the anode side of the device. The paths taken by the charge carriers are schematically illustrated in Figure 2 by arrows. It can be seen that the current in passing the trenches 6 and 7 is compelled to ma~e a detour which leads it into the weakly doped, inner region of ~he base zone 3~
The trenches 6 and 7 are for this purpose made at least as - . . : - . . : . , - - :. - . . . -.. -. ~ ' ., '' .
- - ~ .
deep as the emitter zone 2. They can be produced, for example, by etching in combination with a known photo-resist technique. The photo-current produced flows, by-passing the trenches 6 and 7, to those parts of the ~mitter electrode 4 which are remote from the region 8, and produces a voltage drop beneath the emitter zone 2.
The photo-current of the light-controllable auxiliary thyristor flows across the projection 10 of the collector C~ electrode 9, which projection is arranged between the ends of the trench 9 ~which is in the ~orm of an annular segment), radlally outwards. This arrangement produces a concentration of the photo-current for the auxiliary thyristor as soon as ~t.exceeds the magnitude necessary for the ignition of the aux~liary thyristor. Then, as a result of the high control current density obtalned by thls concentration, the auxiliary thyristor ~s switched on with a relat~ely short ~gnit~on delay t~me. The collector electrode 9 is not absolutely necessary for the functioning of the auxiliary thyristor;
~ ~t ~s, however, expedient to provide an electrode corres-ponding to the pro~ection 10 in order that the photo-current can flow uniformly to the auxiliary emitter zone 2.
In the modif~cation shown in Figure 4, the base zone belcw the re~ion 8 intended to be exposed to light is arranged to be thinner ~han the remainder of the base zone 3.
In order to further increase the ignition sensitivity.of the auxiliary thyristor, a further trench 17 is arranged between the collector electrode 9 and the emitter zone 2 The fundamental difference between the embodiment illustrated in Figures 5 and 6 and that illustrated in - 7-- .
- ' '- - ' ~ - ' :
. . , - ~ :
- . , -~ . ~ . ' -' ' ':
. . -. . . ~ -?
Figures 1 to 3 is that the main emitter zone 1 now serves as a further auxiliary emitter zone and on that side of the emitter zone 1 remote from the region 8 there is provided a third emitter zone 13 which now forms part of a main thyristor. The emitter zone 13 is provided with an electrode 14. The outer periphery of the auxiliary emitter electrode 4 has a segmental project~on 15 which is locaf ed between the ends of the trench 6. By means of the segmental ( ~ projection 15, it is possible to obtain a concentration of the control current for the second auxiliary thyristor (of which the emitter zone 1 forms part) which is thus able to ignite in the above-described manner with a short ignition delay time.
The length of the segmental projections 10 and 15 can be varied to set the effecti~e edge length of the emitter zones ~ and 2, i.e. the length of their p-n ~unctions on the side facing the region 8 t and thus to determine the switch-on --j characteristics of the light-controllable auxiliary thyristor and the second auxiliary thyristor~ If the ratio of the effective edge lengths of the emitter zone 2 on the side facing the region 8 to the ef ecti~e edge length of the emitter zone 1 on the side facing the region 8 is made less than 3:1 (for example, in the embodiment illustr~ted in Figure 5, it is approximately 1:1) it is possible for the light-controllable auxiliary thyristor to operate simply as a current amplifier, i.e. not to ignite. This has the advantage that no load current channel can form during the -- swi~ching-on process in the light-controllable auxiliary thyristor.
. ~ .
. . ... .. , : .
., . - .
- . .--. :. - '. . : ' .. ..
Flgures 7 and 8 illustrate an embodiment in which the region 8 intended to be exposed to light forms part of the surface of the auxiliary emitter zone 2. In this case, the trench 7 constricts the auxiliary emitter zone 2 to form a bridge-piece i6 which is adjoined by the two arms 11. The holes which are produced in this case~ as indicated by the arrows in Figure 8, take a path a~ right-angles to the thickness of the auxiliary emitter zone 2, beneath the latter, and bypassing the trench 6 and 7, flow to the emitter ~-- 10 electrode 4 and thence to the emitter zone 1 which can form part of an auxiliary thyristor, or a main thyristor.
In the exemplary embodiments illustrated, the trenches have been shown as forming segments of an annulus~ This form is advisable when the region 8 intended to ~e exposed to light occupies a central position. However, the trenches can also have other forms and can, for example, run in the radial direction. }t is also possible to use trenches having the shape of an annular segment together with radial ~-; trenches. The trenches can also be arranged with respect to one another in such a way that one or more narrow arms of the auxiliary emitter zone 2 remains between them. The trenches can be filled with electrically insulating material or a h~ghly-resistive material.
.
~ , .
_ g _ - ~ . : . ,: .. -, . . . .
.
., - . ~
- - : ~ ' . ~ . :
: - , ,
Such a thyristor is already known. It consists basically of two parts, one of which is in the form o~ a light-controllable auxiliary thyristor and the other 2 main thyristor. The light-controllable auxiliary thyr~stor serves as a control current amplifier for the main thyristor whicn carries the load current after ignition has been initiated.
If desired, a further auxiliary thyristor can be located between the light-controllable auxiliary thyristor and the ma~n thyristor.
When the surface region which is intended to be expose~ to light ~n use, is in fact illuminated, the photo-current of the light-controllable auxiliary thyristor is arranged to flow into an electrode (known as a collector electrode) which contacts this region, whence it flows in t~e radial direction to the emitter of the auxiliary thyristor and that of the main thyristor. If the emitter-base voltage exceeds a specific value, for example, 0.5 V, at a point on the p-n junction between the base zone and the .. ~.
-.
.. ' ~.
. . ' , -emitter zone of the auxiliary thyristor or of the main thyristor, the thyristor in question ignites.
In practice, it is desira~le to dri~e the light-controllable auxiliary thyristor via light conductors.
Such light conductors normally have a diameter of 1 mm or less. In order to achieve a good du/dt stability which is dependent upon, inter alia, the conductivity of the base zone, the diameter of the region intended to be exposed to light should, on the one hand, be arranged to be only just . ~ , .
sufficiently greater than the diameter of the light conductor to enable it to be contacted. In order that the least possible light power has to be used, the sensitivity of the light-controllable auxiliary thyristor should, on the one hand, be high. The light sensitivity can be increased, for example, by providing the base zone with a high specific res~stance-by means of low doping so that even with low current values, the voltage drop required for ignition is obtained.
i- It is an ob~ect of the present invention to pro~ide a thyristor of the above_mentioned type in which whilst the base zone has a high degree of doping where required, the auxiliary thyristor has a high light sensiti~ity.
According to the invention, there is provided a light-controllable thyristor having a semiconductor body with cathode and anode faces, said body compricing a ~athode-s-de :
base zone the doping of which is reduced in a region adjacent the anode side thereof, a main emitter zone located in said base zone at said cathode face, a region at said cathode face intended to be exposed to light during operation of the thyristor, and an auxiliary emitter zone located in the base zone at said cathode face between said main emitter zone and said region, said main emitter and auxiliary emi~ter zones being provided with main emitter and auxiliary emitter electrodes respectively, said auxiliary emitter electr~de also contacting said base zone; wherein at least one trench is pro~ided on ~he cathode face of said body extending into said base zone and having a depth at ^~ least equal to that of said auxiliary emitter zone, said trench bounding the periphery of said auxiliary emitter - zone facing said main emitter zone and serYing to separate a part of said auxiliary emitter electrode which contacts sa~d auxiliary emitter zone from a part thereof which contacts said base zoneO
- The invention will now be further described with reference to the drawings, in which :-~igure 1 is a schematic plan view of the cathode s~de . of a semiconductor body of a first exemplary embodiment of the invention;
Figure 2 is a section taken along the line II-II o~
Figure 1;
F~gure 3 is a section taken along the line III-I}I of Figure 1;
Figure 4 is a schematic side-sectional part of a second exemplary embodiment of the invention;
Figure S is a schematic plan view of the cathode side of a semiconductor body of a ~hird e~empl~ry embodiment o~ the invention;
y _ ' -- - - .- - - . ~ -. - .
. .' '- . -- ' '" ' ~ ~ :: ' ' ' -- . . . ~ . ~
~ ~31~
P~gure 6 $s a section taken along the line VI-VI
of Figure 5;
Figure 7 ~s a schematic plan view of the cathode side of a semiconductor body of a fourth exemplary embodiment of the invention; and Figure 8 is a section taken along the line VIII-VIII
of Figure 7.
In the various Figures, like elements (either in f~ structure or in function) ha~e been indicated by the same reference numeral. In the plan views, Figures l, 5 and 7, the electrodes ha~e been shown shaded for the sake of lmproved clarity.
The sem~conductor body shown in Figure l has a main emitter zone l, an auxiliary emitter zone 2 and a base zone lS 3 whi~h is common to the two emitter zones and the doping of which decreases with d~stance from the cathode surface of ~he ~ body. The auxiliary emitter zone 2 forms a part of a light-; ~ ~ controllable auxlliary thyristor, whilst the main emitter zone ~ forms part of a main thyristor. The main emitter zone 1~is contacted by means of an emitter electrode 5, and the~auxiliary emitt zone 2 by means of an auxiliary emitter electrode 4. The base zone 3 has a region 8 which is exposed at the surface and is intended to be exposed to light in use of the device. This region 8 is surrounded by an annular collector ~electrode g, the outer periphery of which ha a projecting portion 10 in the form of a segment of a circle.
The auxiliary emltter zone 2 in plan view is in the fonm of a segment of an annulus. That part of the auxiliary emitter S -- ~ ' :' . :
- . . : : . ~
, , .: .. :; . , . - . . --. .. ~ . . . .
electrode 4 which contacts the auxiliary emitter zone 2 is separated from that part of the auxiliary em~tter electrode 4 which contacts the base zone 3 by a trench 6, which also has the shape of a segment of an annulus, along a part of the periphery of the aux1liary emitter zone 2.
Between the region 8 o~ the surface of the base zone 3 which is intended to be exposed to light and the emitter electrode 4, there is located a further trench 7 which also has the shape o~ a segment o~ an annulus and the ends of ~0 which overlap with the respective ends of the trench 6 and of the emitter zone 2. The part of the auxiliary emittPr zone 2 carrying that part of the auxiliary emitter electrode 4 which also contacts the base zone 3 forms arms ~1 wnich are bounded on their opposite ~ides by the trenches 6 and 7.
lS The inner periphery of the trench 7 lies along the outer periphery of the part ~f the collector electrode 9 not provided with the pro~ection 10.
When the region 8 is expose~ to light, pairs of charge - carriers are produced in the base zone 3, and, w~th the indicated negati~e polarity of the emitter electrode 5, the holes f~rst flow towards the surface of the region 8 and then radi~lly outwards, whilst the electrons are dr~wn away to the anode side of the device. The paths taken by the charge carriers are schematically illustrated in Figure 2 by arrows. It can be seen that the current in passing the trenches 6 and 7 is compelled to ma~e a detour which leads it into the weakly doped, inner region of ~he base zone 3~
The trenches 6 and 7 are for this purpose made at least as - . . : - . . : . , - - :. - . . . -.. -. ~ ' ., '' .
- - ~ .
deep as the emitter zone 2. They can be produced, for example, by etching in combination with a known photo-resist technique. The photo-current produced flows, by-passing the trenches 6 and 7, to those parts of the ~mitter electrode 4 which are remote from the region 8, and produces a voltage drop beneath the emitter zone 2.
The photo-current of the light-controllable auxiliary thyristor flows across the projection 10 of the collector C~ electrode 9, which projection is arranged between the ends of the trench 9 ~which is in the ~orm of an annular segment), radlally outwards. This arrangement produces a concentration of the photo-current for the auxiliary thyristor as soon as ~t.exceeds the magnitude necessary for the ignition of the aux~liary thyristor. Then, as a result of the high control current density obtalned by thls concentration, the auxiliary thyristor ~s switched on with a relat~ely short ~gnit~on delay t~me. The collector electrode 9 is not absolutely necessary for the functioning of the auxiliary thyristor;
~ ~t ~s, however, expedient to provide an electrode corres-ponding to the pro~ection 10 in order that the photo-current can flow uniformly to the auxiliary emitter zone 2.
In the modif~cation shown in Figure 4, the base zone belcw the re~ion 8 intended to be exposed to light is arranged to be thinner ~han the remainder of the base zone 3.
In order to further increase the ignition sensitivity.of the auxiliary thyristor, a further trench 17 is arranged between the collector electrode 9 and the emitter zone 2 The fundamental difference between the embodiment illustrated in Figures 5 and 6 and that illustrated in - 7-- .
- ' '- - ' ~ - ' :
. . , - ~ :
- . , -~ . ~ . ' -' ' ':
. . -. . . ~ -?
Figures 1 to 3 is that the main emitter zone 1 now serves as a further auxiliary emitter zone and on that side of the emitter zone 1 remote from the region 8 there is provided a third emitter zone 13 which now forms part of a main thyristor. The emitter zone 13 is provided with an electrode 14. The outer periphery of the auxiliary emitter electrode 4 has a segmental project~on 15 which is locaf ed between the ends of the trench 6. By means of the segmental ( ~ projection 15, it is possible to obtain a concentration of the control current for the second auxiliary thyristor (of which the emitter zone 1 forms part) which is thus able to ignite in the above-described manner with a short ignition delay time.
The length of the segmental projections 10 and 15 can be varied to set the effecti~e edge length of the emitter zones ~ and 2, i.e. the length of their p-n ~unctions on the side facing the region 8 t and thus to determine the switch-on --j characteristics of the light-controllable auxiliary thyristor and the second auxiliary thyristor~ If the ratio of the effective edge lengths of the emitter zone 2 on the side facing the region 8 to the ef ecti~e edge length of the emitter zone 1 on the side facing the region 8 is made less than 3:1 (for example, in the embodiment illustr~ted in Figure 5, it is approximately 1:1) it is possible for the light-controllable auxiliary thyristor to operate simply as a current amplifier, i.e. not to ignite. This has the advantage that no load current channel can form during the -- swi~ching-on process in the light-controllable auxiliary thyristor.
. ~ .
. . ... .. , : .
., . - .
- . .--. :. - '. . : ' .. ..
Flgures 7 and 8 illustrate an embodiment in which the region 8 intended to be exposed to light forms part of the surface of the auxiliary emitter zone 2. In this case, the trench 7 constricts the auxiliary emitter zone 2 to form a bridge-piece i6 which is adjoined by the two arms 11. The holes which are produced in this case~ as indicated by the arrows in Figure 8, take a path a~ right-angles to the thickness of the auxiliary emitter zone 2, beneath the latter, and bypassing the trench 6 and 7, flow to the emitter ~-- 10 electrode 4 and thence to the emitter zone 1 which can form part of an auxiliary thyristor, or a main thyristor.
In the exemplary embodiments illustrated, the trenches have been shown as forming segments of an annulus~ This form is advisable when the region 8 intended to ~e exposed to light occupies a central position. However, the trenches can also have other forms and can, for example, run in the radial direction. }t is also possible to use trenches having the shape of an annular segment together with radial ~-; trenches. The trenches can also be arranged with respect to one another in such a way that one or more narrow arms of the auxiliary emitter zone 2 remains between them. The trenches can be filled with electrically insulating material or a h~ghly-resistive material.
.
~ , .
_ g _ - ~ . : . ,: .. -, . . . .
.
., - . ~
- - : ~ ' . ~ . :
: - , ,
Claims (11)
1. A light-controllable thyristor having a semi-conductor body with cathode and anode faces, said body comprising a cathode-side base zone the doping of which is reduced in a region adjacent the anode side thereof, a main emitter zone located in said base zone at said cathode face, a region at said cathode face intended to be exposed to light during operation of the thyristor, and an auxiliary emitter zone located in the base zone at said cathode face between said main emitter zone and said region, said main emitter and auxiliary emitter zones being provided with main emitter and auxiliary emitter electrodes respectively, said auxiliary emitter electrode also contacting said base zone; wherein at least one trench is provided in the cathode face of said body extending into said base zone and having a depth at least equal to that of said auxiliary emitter zone, said trench bounding the per-iphery of said auxiliary emitter zone facing said main emitter zone and serving to separate a part of said auxiliary emitter electrode which contacts said auxiliary emitter zone from a part thereof which contacts said base zone.
2. A thyristor as claimed in Claim 1, wherein at least a part of said auxiliary emitter zone is bounded on opposite sides by said trench or trenches.
3. A thyristor as claimed in Claim 2, wherein said auxiliary emitter zone and said trench are each in the form of an annular segment; and wherein a further trench in the form of an annular segment is arranged to partly surround said region in such manner that only the ends of said further trench overlap with the respective ends of said first-mentioned trench and said auxiliary emitter zone, said auxiliary emitter zone having a respective arm at either end bounded on opposite sides by said trenches.
4. A thyristor as claimed in Claim 3 wherein said region is surrounded by an annular collector electrode which contacts said base zone.
5. A thyristor as claimed in Claim 4, wherein said collector electrode has a segmental projection lying between the ends of said further trench.
6. A thyristor as claimed in Claim 1, wherein a third emitter zone is arranged on that side of said main emitter zone which faces away from said region.
7. A thyristor as claimed in Claim 3, wherein said auxiliary emitter electrode is of annular formation and has a segmental projection on its outer periphery which lies between the ends of said first-mentioned trench.
8. A thyristor as claimed in Claim 7, wherein said region is constitut-ed by a part of the surface of the base zone where the thickness of the base zone is less than at other points where the base zone extends to the surface of said body.
9. A thyristor as claimed in Claim 8, wherein said region is constitut-ed by part of the auxiliary emitter zone.
10. A thyristor as claimed in Claim 9, wherein the effective lengths of the peripheries of the main emitter zone and the auxiliary emitter zone at the sides of said zones facing said region have a ratio greater than 1:3.
11. A thyristor as claimed in Claim 3, wherein said two trenches are interconnected.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2715482.1 | 1977-04-06 | ||
| DE19772715482 DE2715482C2 (en) | 1977-04-06 | 1977-04-06 | Thyristor controllable with light |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1113190A true CA1113190A (en) | 1981-11-24 |
Family
ID=6005816
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA300,385A Expired CA1113190A (en) | 1977-04-06 | 1978-04-04 | Light-controllable thyristors |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS6022830B2 (en) |
| CA (1) | CA1113190A (en) |
| DE (1) | DE2715482C2 (en) |
| FR (1) | FR2386906A1 (en) |
| GB (1) | GB1563689A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5998556A (en) * | 1982-11-26 | 1984-06-06 | Mitsubishi Electric Corp | Phototrigger thyristor |
| JPS6064469A (en) * | 1983-09-19 | 1985-04-13 | Hitachi Ltd | Photo thyristor |
| EP0304032B1 (en) * | 1987-08-20 | 1993-01-27 | Siemens Aktiengesellschaft | Light controlled thyristor |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3731162A (en) * | 1969-09-25 | 1973-05-01 | Tokyo Shibaura Electric Co | Semiconductor switching device |
| JPS50123282A (en) * | 1974-03-15 | 1975-09-27 | ||
| DE2458401C2 (en) * | 1974-12-10 | 1982-06-24 | Siemens AG, 1000 Berlin und 8000 München | Thyristor controllable with light |
-
1977
- 1977-04-06 DE DE19772715482 patent/DE2715482C2/en not_active Expired
-
1978
- 1978-03-31 FR FR7809529A patent/FR2386906A1/en active Granted
- 1978-04-04 CA CA300,385A patent/CA1113190A/en not_active Expired
- 1978-04-05 GB GB1323078A patent/GB1563689A/en not_active Expired
- 1978-04-05 JP JP53040166A patent/JPS6022830B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2715482A1 (en) | 1978-10-12 |
| JPS6022830B2 (en) | 1985-06-04 |
| FR2386906A1 (en) | 1978-11-03 |
| JPS53125783A (en) | 1978-11-02 |
| GB1563689A (en) | 1980-03-26 |
| DE2715482C2 (en) | 1985-06-13 |
| FR2386906B1 (en) | 1984-09-07 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |