US3261985A

US3261985A - Cross-current turn-off silicon controlled rectifier

Info

Publication number: US3261985A
Application number: US246446A
Authority: US
Inventors: Somos Istvan
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-12-21
Filing date: 1962-12-21
Publication date: 1966-07-19
Anticipated expiration: 1983-07-19
Also published as: DE1295695B; FR1397205A

Description

July 19, 1966 l. soMos 3,261,985

CROSS-CURRENT TURN-OFF SILICON COIIROLLED RECTIFIER Filed Dec. 2l, 1962 2 Sheets-Sheet l GATE ,DR/0R ART v CATHO E GA TE /NVENTORJ [srl/AN SOMOS,

July 19, 1966 l. soMos 3,251,935

CROSS-CURRENT TURN-OFF SILICON CONTROLLED RECTIFIER I v Filed Deo. 21, 1962 2 Sheets-Sheet 2 WML-LAWN GATE N /O' I" /I3 Ym m mi J -AZ /NVEN TOR.

./'sTvA/V Somos,

ATTORNEY.

www /4 P N United States Patent O 3,261,985 CROSS-CURRENT TURN-OFF SILICON CONTRGLLED RECTHFIER Istvan Somos, Drexel Hill, Pa., assignor to General Electric Company, a corporation of New York Filed Dec. 21, 1962, Ser. No. 246,446 9 Claims. (Cl. 307-885) This invention relates to semiconductor devices and, more particularly, to PNPN semiconductor devices of the type that is capable of being switched readily between two extremes of impedance and an object of the invention is the provision of a simple, reliable and improved device of this character.

More specifically, the invention relates to PNPN semiconductor devices of the type known as silicon controlled rectifiers. Such a device typically comprises a body of silicon having a pair of main electrodes, known as anode and cathode, and a control electrode or gate, with three alternately poled PN (rectifying) junctions being disposed in series between the main electrodes. It has the characteristic of being capable of remaining in either a high impedance condition (in which it blocks current in either direction) or a low forward impedance condition (in which it freely conducts conventional current from anode to cathode) without a continuously applied control signal. Silicon controlled rectifiers are functionally similar to gas tube thyratrons, which are capable of controlling large amounts of current by means of relatively small power pulses. Although a silicon controlled rectifier may readily be transferred from the high impedance mode of operation to the low impedance mode in response to the supply of relatively small firing pulses of current to the gate, switching from the low impedance condition to the high impedance condition to effect turnoff is much more difficult. A conventional manner of effecting turnoff of a silicon controlled rectifier has been to apply a reverse voltage to its anode and cathode. This reverse voltage causes a reverse recovery current through the device which removes the carriers from the end junctions of the device in a brief interval, c g., 1 to 5 microseconds. The remaining carriers, particularly those in the vicinity of the middle PN junction, disappear by recombination because the reverse current is terminated when the carrier concentrations at the end junctions reach the equilibrium point. The recombination time is relatively long and makes the turnoff time correspondingly long. If the reverse bias voltage is terminated before recombination has proceeded substantially to completion and forward bias voltage exists across the anode and cathode, the silicon controlled rectifier will break over and start conducting again. Accordingly, a further object of this invention is the provision of a silicon controlled rectifier in which the high impedance condition or blocking state is attained and complete turnofl' effected in a substantially shorter time, i.e., within a few microseconds of initiation of the turnoff operation.

In carrying the invention into elect in one form thereof, the intermediate P zone of a PNPN semiconductor silicon controlled rectifier is provided with an auxiliary electrode of P type conductivity material and the intermediate N type conductivity zone is provided with another auxiliary electrode of N type conductivity material so that these electrodes and the intermediate P and N zones of the P and N device constitute a diode having a rectifying junction in common with the middle rectifying junction of the PNPN device. Connections are provided lfor supplying a reverse voltage to these auxiliary electrodes to cause current through such diode rectifier that crosses the main current path in the device and removes the injected minority carriers from the common middle Patented July 19, 1966 invention, reference should now be had to the following specification and to the accompanying drawings in which:

FIG. 1 is a block layer diagram of a conventional prior art silicon controlled rectifier with characteristic curves of the injected minority carrier concentration within each of the separate P and N zones represented by characteristic curves.

FIG. 2 is a diagram of a PNPN semiconductor silicon controlled rectifier device embodying the invention.

FIG. 3 is a block layer diagram of a portion of a PNPN silicon controlled rectifier embodying the invention with injected carrier concentration within each of the separate P and N zones represented by characteristic curves to facilitate an understanding of the operation of the invention.

FIG. 4 comprises a plan view and a view in front elevation of a PNPN silicon controlled rectifier embodying the invention.

FIG. 5 is a view in elevation, partly in section of a modification and FIG. 6 is a sectional view of another modification.

Referring now to the drawings, and particularly to FIG. 1, a conventional silicon controlled rectifier device 1 is conventionally illustrated as having four zones arranged in succession with contiguous zones of opposite conductivity type so that in order from right to left the Zones are designated PNPN. The junctions between contiguous P `and N zones in order from right to left are denoted J1, J2 and I3. The end P zone functions as an anode and the end N zone functions as a cathode. Connected by ohmic contact to the intermediate P zone is a gate conductor denoted GATE. With the anode connected to the positive terminal of a suitable source and the cathode connected to the negative terminal, forward conduction through the PNPN silicon controlled rectifier can be initiated by supplying a firing pulse of current to the gate contact to switch the device from the blocking state to the conducting state. During its normal conducting state the forward current is in the direction of the arrow designated If and the distribution of injected minority carrier concentration in the forward direction in the four zones is represented by the solid line curves 2, 3, 4 and 5. The P equilibrium value in the internal N zone is represented by the horizontal line 6 and the N equilibrium value in the internal P zone is represented by the horizontal line 7.

Conventional practice in turninor off the silicon controlled rectifier has been to apply a negative bias voltage or Iin other words to reverse the polarity of the voltage supplied to the anode and cathode. When this reverse voltage is applied, the holes and electrons in the vicinity of the two end junctions J1 and .T3 (RFIG. 1) diff-use to these junctions and produce a reverse (recovery) current in the external circuit that is represented by the arrow designated Ir. The directions of movement of the injected minority carriers in the intermediate P and N zones during this process of removal from the end juncftions is represented by the arrows in the shaded areas. Within one or two microseconds after the application of the reverse voltage this reverse current fr sweeps the injected minority carriers from the end junctions .T1 and J3. The carrier distribution in the intermediate N zone is then represented by the broken line curve 8 and the carrier distribution in the intermediate P zone is represented by the broken line curve 9. Thus, as indicated by these carrier distribution curves the concentration of injected carriers at the end junctions I1 and I3 is reduced to the equilibrium value. This is accomplished within a few microseconds of the application of reverse bias voltage and these junctions then assume a blocking state. Recovery of the silicon controlled rectifier is not complete, however, because there is still a high concentration of injected minority carriers in the vicinity of the middle junction J2. All these carriers represented by the shaded areas under curves S and 9 must disappear by recombination because the reverse (recovery) current ceases when injected minority carriers are swept out of rthe end junctions I1 and J3 and the carrier distribution at these junctions attains equilibrium value. After the hole `and electron distribution at junction J2 has decreased to a low value as a result of the recombination process, this junction regains its blocking state and a forward voltage may be applied to the silicon controlled rectifier without causing it to turn on. However, this recombination process takes a relatively long time, eg., between 10 and microseconds and this makes the turnoff time correspondingly long. In certain applications, such for example as high frequency inverters a long turnoff time is disadvantageous.

The present invention greatly reduces the t-urnoff time, e.g., it reduces it to the order of one or two microseconds. In the embodiment of this invention that is diagrammatically represen-ted in FIG. 2, the four zone semiconductor device 16 has an intermediate P zone 11 and an intermediate N zone 12. These zones and the junction between them may be formed from a wafer of silicon by any suitable method such, for example, as precision gaseous diffusion techniques. In a fairly typical device the thickness of this wafer may be approximately 10 mils and its diameter may be in the neighborhood of 1.5 centimeters. On a portion of the :dat outer surface of the P zone 11 is formed a zone 13 of N type conductivity, and on a portion of the parallel outer surface of the intermediate N zone 12 in register with the opposite end N zone 13, there is disposed an auxiliary zone 14 of N type conductivity.

Zones

13 and 14 may be formed of any suitable material and in any appropriate manner, e.g., they m-ay be formed of gold foil plus antimony and may be formed on the surfaces of

zones

11 and 12 by alloying the gold foil plus antimony strip into the surfaces of the silicon wafer or by any other suitable method. These

zones

13 and 14 may also be formed by gaseous diffusion and masking techniques or by the vapor deposition method th-at is known in the art as the epitaxial process.

On another portion of the iiat outer surface of P zone l11 is formed an auxiliary zone 15 of P type conductivity; similarly on the exposed lower surface of N zone 12 is formed a Zone 16 of P type conductivity in register with the auxiliary P zone 15. Consequently, as is shown in FIG. 2, the end P zone 16 of my invention is laterally offset with respect to the end N zone 13. The P zones I15 and 16 may be formed in any suitable manner. For example, they may be formed by alloying aluminum strip into the exterior surfaces of the silicon wafer, i.e.,

zones

11 and 12 or by utilizing diffusion and masking or epitaxial processes. A g-ate conductor, designated GATE is connected to the P conductivity type zone 11. in some cases with the use of appropriate circuitry the auxiliary P zone 15 may be used as the gate contact.

The

zones

16, 12, 11 and 13 constitute a four zone PNPN semiconductor device and together with the gate constitute a silicon controlled rectifier of which the end P type conductivity zone 16 constitutes the anode and the end N type conductivity zone 13 constitutes the cathode. This rectifier has three alternately poled rectifying junctions J1, J2 and 13 in series between anode and cathode. For conduction in the forward direction, the anode 16 is connected to the positive terminal of a supply source 17 and t-he cathode 13 is connected through a load 18 to the negative terminal of the source, whereby forward voltage is supplied to the terminal zones of the rectifier. Conduction of main or load current by the PNPN silicon controlled rectifier is initiated by supplying a firing pulse of current to the GATE. For this purpose, as is well known in the art, suitable external triggering means (not shown) can be connected between the intermediate P zone 11 and the cathode 13. Due to the laterally offset arrangement of the anode 16 and the cathode 13, the main current conduction takes place in a diagonal direction through the silicon controlled rectifier from the anode 16 at the lower right hand corner of the device through N type zone 12, P type zone 11 to the cathode 13 in the upper left hand corner of the device This forward current traverses an appreciable area in the midsection of the middle NP junction J2 of the device 10 in the direction generally indicated by the arrow If.

The auxiliary N type zone 14, N type zone 12, P type zone 11 and auxiliary P type zone 15 constitute a PPNN semiconductor device which in practical effect is a PN diode having a single rectifying junction J2 in common with the middle junction J2 of the PNPN device. The

auxiliary zones

14 and 15 have been so arranged that this PPNN diode device provides an auxiliary conducting path along a diagonal that crosses the diagonal main conducting path of the PNPN device. In this diode device the auxiliary N type Zone 114 and the auxiliary P type zone 15 serve as turnofr electrodes having terminals which may be connected through an external diode rectifier 19 and the conductor 2t) to a suitable source of direct voltage that is represented by supply terminals 21. A suitable switching device 22 is included in these connections.

As shown, the diode rectifier 19 in the external circuit is connected to conduct in the direction of reverse current through the

PN diode

15, 11, 12, 14. This reverse current is represented by the arrow Ic. It will be noted that both the auxiliary current Ic, which flows in a reverse sense between the P and N

auxiliary electrodes

15 and 14 of the diode rectiiier, and the main current If, which iiows in a forward sense between the anode 16 and the cathode 13 of the PNPN device, pass through the common junction J2 from zone 12 to zone 11 in the same electrical direction but on cross diagonal paths, with the auxiliary current crossing the main current over the whole area of J2 that is traversed by the latter. Typically, the voltage source 17 for the PNPN silicon controlled rectitier may be in the neighborhood of 400 volts whereas the voltage of source 21 for the PPNN diode device may be a Very much lower value.

To turn on the PNPN silicon controlled rectifier 10 with forward bias voltage being supplied from the source 17 through the load to the anode 16 and cathode 13, a pulse of firing current is supplied to the GATE from external triggering means. This causes the PNPN path to switch from its high impedance to its low impedance state and to become conducting in the forward direction with the result that forward current is supplied to the load 18. During conduction in the forward direction the distribution of injected carriers in the individual

P-N-P-N zones

15, 12, 11 and 13 respectively is represented in the concentration diagram in FIG. 3 by the solid line curves 23, 24, 2S and 26 respectively. A comparison of FiIG. 3 and FIG. 1 indicates that the concentration distribution of injected carriers during normal main current conduction in the forward direction is essentially the same as in the case of the conventional silicon controlled rectifier.

To turn ofi the PNPN silicon controlled rectifier 10, i.e., to enable the PNPN path through

zones

16, 12, 11 and 13 to regain forward blocking ability, the switching device 22 is closed to apply a reverse bias voltage across the

PPNN diode

15, 11, 12, 14. This immediately results in an auxiliary current Ic in the diagonal diode path having the same electrical direction across the middle junction J2 as the main current If then iiowing in the PNPN silicon controlled rectifier path. The current Ic, which is a reverse current in `the diode path, effects a net removal of the injected minority carriers from the NP junction J2. The directions of movement of the carriers in this removal process from the middle junction are represented by the arrows 27 in the shaded areas of the intermediate P and N zones in FIG. 3. As shown, the directions are oposite to the directions represented by the arrows in FIG. 1 produced by the conventional turnoff method. Within a period of approximately one microsecond after initiation of turnoff, the carriers are swept out of the middle junction J2 and the concentration in the intermediate P and

N zones

11 and 12 is represented by the broken line curves 28 and 29. As indicated by these curves the concentration at the middle junction is reduced to the equilibrium values on both sides of this junction and this prepares the junction to regain its blocking ability. However, at this instant recovery of the PNP-N silicon controlled rectifier is not complete owing to the concentration of carriers at the end junctions J1 and J3 as represented by broken line curves 28 and 29. Consequently, the auxiliary current Ic, which is the recovery current for the junction J2, continues until these carriers are all removed and then terminates. Upon termination of the auxiliary current the junction J2 regains its blocking state. Recovery of the PNPN silicon controlled

rectifier

16, 12, 11 and 13 is now complete, and main current conduction will not resume even though the device remains connected to the forward voltage source 17. The time required from initiation of the auxiliary current in the PPNN diode until complete turnoff and recovery of the PNPN silicon controlled rectifier is 'complete is of the order of a few microseconds.

The auxiliary current Ic required to reduce the injected carriers in the intermediate P and

N zones

11 and 12 to equilibrium is very considerably smaller than the forward current If of 'the silicon controlled rectifier. Consequently, a high value forward current can be interrupted by a low value current pulse. For example, a forward current of 200 amperes can be interrupted by a low value current pulse of 20 amperes.

In the form that is illustrated in FIG. 4 the end N type conductivity zone 13 of the PNPN semiconductor device and the additional P type conductivity zone of the PPNN diode device have the form of parallel, closely spaced rectilinear strips that are located on opposite sides of an axis generally perpendicular to the NP junction of the

internal zones

12 and 11 of the device; the end P type conductivity zone 16 (anode) and the additional N type conductivity zone 14 will have the same form.

In the modification that is illustrated in FIG. 5 the end N type conductivity zone 13 (cathode) of the PNPN device has the form of an annulus and the additional end P type conductivity zone 15 of the PPNN device has the form of a circular disk within the annulus 13. Similarly, the additional end N type conductivity zone 14 has .the form of an annulus disposed in register with the cathode 13, and the end P type conductivity zone 16 (anode) has the form of a coaxial disk within the annulus.

In this modification main current traverses a predeter- 'mined annular area of the middle junction J2 of the PNPN silicon controlled rectifier device in the direction represented by the arrows If. The reverse current of the -PPNN diode path takes place in the same electrical 'direction across the same annular area of the common middle junction J2 on a cross diagonal axis as indicated :by the arrow Ic. Instead of being in the form of disks `the

zones

15 and 16 may be in the form of rings as illustrated in the modification of FIG. 6. The operation of the modifications illustrated in FIGS. 5 and 6 is the same as described in connection With FIG. 2.

The device may also be utilized in present inverter 'circuits in which turnof in each cycle is effected by applying a reverse bias voltage to the anode and cathode.

When thus used a constant D.-C. bias voltage will be applied to the

diode electrodes

14 and 15. In this case, owing to the reverse bias voltage applied to the anode and cathode the turnoif is in accordance with the process herein described and referred to as the conventional process. However, .the turnolf time will be reduced t0 the range of 5-10 microseconds or less.

The device may also be used, with appropriate circuitry,

as a square wave generator. For this purpose, an adjustable impedance 23 is included in series relationship in the PPNN diode circuit. By adjusting this impedance the current Ic may Ibe adjusted to a value less than the critical value required to effect complete turnof action.

As a result, retiring of the device occurs after interruption of the forward current and this procedure is repeated continuously to provide continuous oscillation.

Alterations and modificationswill readily suggest themselves to persons skilled in the art without departing from the true spirit of this invention or from the scope of the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A semiconductor translating device comprising:

(a) a circular semiconductor single crystal silicon Wafer having a main P type conductivity zone and a contiguous main N type conductivity zone in flat face to at face contact,

(1b) the exterior at face of each of said main zones :being provided with a radially centrally disposed zone of one type conductivity and a surrounding concentric annular zone of the opposite type conductivity to constitute (1) a PNPN semiconductor device with the terminal P and N zones constituting -an anode and -a cathode respectively and (2) a PPNN semiconductor device having terminal electrodes and a PN junction in common with the middle junction of said PNPN semiconducltor device,

(c) one of said main zones of said PNPN device being provided with means for receiving a pulse of firing current to initiate conduction through said PNPN device, and

(d) means for supplyin-g a voltage to said terminal electrodes of said PPNN device to cause a reverse current through said PPNN device when said PNPN device is conducting to remove injected carriers from said common junction to terminate conduction through said PNPN device.

2. A semiconductor translating device comprising:

(a) a semiconductor body including four zones arranged in succession with contiguous zones of opposite conductivity type to constitute a PNPN semiconductor device having three PN junctions disposed in generally parallel planes and having an axis that is perpendicular to all of said planes, with the end P and N zones of said PNPN device being respectively located on opposite sides of said axis,

(b) the intermediate P zone of said PNPN device being provided with means to receive firing current to turn on said PNPN device,

(c) the intermediate P and N zones of said PNPN device each bein-g provided with a turnoff electrode on the opposite side of said axis from the corresponding end zone of said PNPN device thereby to provide a diode rectifier having a single rectifying junction that is in common with the middle PN junction of said PNPN device and having a conducting path that crosses the conducting path between the end zones of said PNPN device and (d) said turnof electrodes being adapted to receive a voltage having a polarity to cause a reverse current through said diode when said PNPN device is conducting vto remove injected carriers from said common junction thereby to turn off said PNPN device.

3. A semiconductor translating device comprising:

(a) a semiconductor body having a Wafer-like zone of P type conductivity and a contiguous wafer-like zone of N type conductivity in at tace to flat face contact to form an internal PN junction therebetween, said body having an axis of symmetry that is generally perpendicular to said junction,

(b) each of said zones having an exterior at face disposed parallel 'to said internal PN junction and provided With two parallel strip zones of opposite conductivity types with the P type strip zones arranged on one side of said axis and the N type strip zones arranged on the opposite side of said axis thereby to constitute (l) a PNPN semiconductor device and `(Il) a PN diode provided with P and N type conf ductivity turnoff electrodes and having a PN junction in common with said internal junction of said PNPN device and a conducting path that crosses the conducting path of said PNPN device,

(c) one of the zones of said PNPN device being provided with means for receiving a pulse of firing current to initiate conduction through said PNPN device, and

(d) terminals connected to said turnof electrodes and adapted to be connected to a source for supplying to said turno electrodes a voltage having a polarity for causing a reverse current through said diode to remove injected carriers from said common junction to effect turnot of said PNPN device.

4. A semiconductor translating device comprising:

(a) a circular semiconductor body having a waferlike P type conductivity zone and a contiguous Waferlike zone of N type conductivity in flat face to flat face contact,

(b) the exterior at face of both of said zones being provided with an inner annular zone of one type conductivity and an outer concentric zone of the op posite type conductivity thereby to constitute (l) a PNPN semiconductor device and y(2) a PN diode device having turnof electrodes and having a PN junction in common with the middle junction of said PNPN device and a conducting path that crosses the conducting path of said PNPN device (c) said Wafer-like P zone of said PNPN device being provided with means for receiving a pulse of firing current to initiate conduction through said PNPN device, and

(d) terminals connected to said turnoff electrodes and adapted to be connected to a source for supplying to said turnott" electrodes a voltage having a polarity to cause reverse current through said diode to remove injected carriers from said middle junction to efect turno of said PNPN device.

5. A semiconductor rectifier comprising:

(a) a semiconductor body having a wafer-like zone of P type conductivity and a contiguous wafer-like zone of N type conductivity in face-to-face contact to form -an internal PN junction therebetween, said P zone and said contiguous N zone respectively having outer surfaces that are generally fiat and parallel to each other;

(b) a iirst portion of the outer surface of said P zone being provided with an end zone of N type conductivity and a first portion of the outer surface of said contiguous N zone being provided with an end zone of P type conductivity to form a PNPN semiconductor device, With the end P zone and the end -N zone constituting main electrodes of said PNPN device;

(c) means connected across at least one of the PN junctions of said PNPN device for initiating main current conduction through said PNPN device;

(d) a second portion of said outer surface of the rst mentioned P zone being provided with a first auxiliary electrode and a second portion of said outer surface of the contiguous N zone being provided with a second .auxiliary electrode to form a PN diode whose PN junction is in common with the internal PN junction of said PNPN device, said PN diode providing between said auxiliary electrodes a conducting path for auxiliary current that crosses the main current in said PNPN device; and

(e) means connected to said auxiliary electrodes for initiating auxiliary current conduction in a reverse direction through said P-N diode to remove injected carriers from said common middle junction to effect turnof of said PNPN device.

6. The rectifier of claim 5 in which said end N zone is laterally offset with respect to said end P zone and in register with said second auxiliary electrode, and in which said first auxiliary electrode is laterally offset with respect to said second auxiliary electrode and in register with said end P zone.

7. For use in combination with a load current circuit, a firing current circuit, and a turnoi current circuit, a semiconductor translating device comprising:

(a) a semiconductor -body including four zones arranged in succession with contiguous zones being of opposite conductivity types to provide a PNPN semi- `conductor device having a PN junction, an NP junc tion, and another PN junction in series between the terminal P and N zones there-of;

(b) means for serially connecting said terminal P and `N Zones in the load current circuit, whereby load *current can flow in a forward direction between said terminal P zone and said terminal N zone when the PNPN device is turned on;

(c) means for interconnecting one of said four zones 'of said body and the tiring current circuit to supply a firing current to turn on the PNPN device;

(d) a pair of auxiliary electrodes respectively connected to the intermediate P and N zones of said body to Iprovide therewith a diode rectifier having a single rectifying junction that is in common with said fNP junction of the PNPN device, said auxiliary electrodes being so arranged that reverse current therebetween crosses said load current over the whole NP junction area that is traversed by said load current; and

(e) means for serially connecting said auxiliary elec trodes in the turnoff current circuit, the latter means being so arranged that the turnoi current will flow in a reverse direction through said `diode rectifier to remove injected carriers from said common NP junc tion to effect turnoff of the PNPN device.

8. The semiconductor translating device of claim 7 in which the means for interconnecting one of said four zones of said -body and the tiring current circuit comprises a gate contact connected to the intermediate P zone of saidbody.

9. For use in combination with a rst voltage source having relatively positive and negative terminals and a second voltage source having relatively ypositive and negative terminals, a semiconductor translating device comprising:`

(a) a semiconductor body including four zones arranged in succession with contiguous zones 'being of opposite conductivity types to provide a three-junction PNPN semiconductor device, the terminal P and N zones of said body, respectively constituting anode and cathode of the device, being laterally offset with respect to each other;

(b) Ymeans for connecting said anode to a positive terminal of the tirst voltage source and said cathode to a negative terminal of the tirst voltage source;

(c) first and second turno electrodes respectively connected to the intermediate IP and N zones of said body to provide therewith a diode rectifier having a PN rectifying junction in `common with the middle junction of the PNPN device, said rst turnofrr electrode 'being formed by P type conductivity material and being disposed in register with said anode, and said second turnoff electrode being formed by N type conductivity material and being disposed in register with said cathode; and

(d) means for connecting said rst turnoff electrode to a negative terminal of the second voltage source and said second turnoff electrode -to a positive terminal of -the second voltage source to vcause a reverse current through said diode rectier thereby to remove injected carriers from said common middle junction to eiect turno action of Ithe PNPN device.

References Cited bythe Examiner UNITED STATES PATENTS OTHER REFERENCES Unique Properties of the Four-Layer Diode, by Shookley; Electronics Industries and Tele-Tech, August 1957, page 60.

JOHN W. HUCKERT, Primary Examiner.

I. D. CRAIG, Assistant Examiner.

Claims

1. A SEMICONDUCTOR TRANSLATING DEVICE COMPRISING: (A) A CIRCULAR SEMICONDUCTOR SINGLE CRYSTAL SILICON WAFER HAVING A MAIN P TYPE CONDUCTIVITY ZONE AND A CONTIGUOUS MAIN N TYPE CONDUCTIVITY ZONE IN FLAT FACE TO FLAT FACE CONTACT, (B) THE EXTERIOR FLAT FACE OF EACH OF SAID MAIN ZONES BEING PROVIDED WITH RADIALLY CENTRALLY DISPOSED ZONE OF ONE TYPE CONDUCTIVITY AND A SURROUNDING CONCENTRIC ANNULAR ZONE OF THE OPPOSITE TYPE CONDUCTIVITY TO CONSTITUTE (1) A PNPN SEMICONDUCTOR DEVICE WITH THE TERMINAL P AND N ZONES CONSTITUTING AN ANODE AND A CATHODE RESPECTIVELY AND (2) A PPNN SEMICONDUCTOR DEVICE HAVING A TERMINAL ELECTRODES AND A PN JUNCTION IN COMMON WITH THE MIDDLE JUNCTION OF SAID PNPN SEMICONDUCTOR DEVICE, (C) ONE OF SAID MAIN ZONES OF SAID PNPN DEVICE BEING PROVIDED WITH MEANS FOR RECEIVING A PULSE OF FIRING CURRENT TO INITIATE CONDUCTION THROUGH SAID PNPN DEVICE, AND (D) MEANS FOR SUPPLYING A VOLTAGE TO SAID TERMINAL ELECTRODES OF SAID PPNN DEVICE TO CAUSE A REVERSE CURRENT THROUGH SAID PPNN DEVICE WHEN SAID PNPN DEVICE IS CONDUCTING TO REMOVE INJECTED CARRIERS FROM SAID COMMON JUNCTION TO TERMINATE CONDUCTION THROUGH SAID PNPN DEVICE.