Granted Patent B2

US 9,941,439 · App. 14/922,809 · Granted Apr 10, 2018

Abstract

Claims (45)

1. A silicon carbide based thyristor having a positive temperature coefficient of forward voltage at a forward current density less than 100 A/cm 2 .

2. The silicon carbide based thyristor of claim 1 , wherein a cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is less than 75 A/cm 2 .

3. The silicon carbide based thyristor of claim 2 , wherein the cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is between 50 A/cm 2 and 75 A/cm 2 .

4. The silicon carbide based thyristor of claim 1 , wherein the silicon carbide based thyristor comprises:

a semiconductor layer having a first conductivity type and a first doping concentration;

a carrier injection layer on the semiconductor layer, the carrier injection layer having the first conductivity type and a second doping concentration that is lower than the first doping concentration, wherein the carrier injection layer has a thickness greater than 1 micron;

a drift layer on the carrier injection layer, the drift layer having the second conductivity type;

a base layer having the first conductivity type on the drift layer; and

an anode region having the second conductivity type on the base layer.

5. The silicon carbide based thyristor of claim 4 , further comprising:

a buffer layer having the second conductivity type between the carrier injection layer and the drift layer, wherein the carrier injection layer and the buffer layer form a p-n junction;

wherein the carrier injection layer is thicker than the buffer layer.

6. The silicon carbide based thyristor of claim 4 , wherein a thickness of the carrier injection layer and the second doping concentration are selected to reduce minority carrier injection by the carrier injection layer in response to an increase in operating temperature of the thyristor.

7. The silicon carbide based thyristor of claim 4 , wherein a thickness of the carrier injection layer and the second doping concentration of the carrier injection layer are selected so that a cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is less than 100 A/cm 2 .

8. The silicon carbide based thyristor of claim 7 , wherein thickness of the carrier injection layer and the second doping concentration of the carrier injection layer are selected so that a the cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is less than 75 A/cm 2 .

9. The silicon carbide based thyristor of claim 7 , wherein thickness of the carrier injection layer and the second doping concentration of the carrier injection layer are selected so that a the cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is between 50 A/cm 2 and 75 A/cm 2 .

10. The silicon carbide based thyristor of claim 4 , wherein the base layer comprises a main base layer and an assistant base layer that is isolated from the main base layer by a trench, the thyristor further comprising an assistant anode region on the assistant base layer and having the second conductivity type, and a conductive interconnect between the assistant anode region and the main base layer.

11. An optically triggered thyristor, comprising:

a primary thyristor including a base layer; and

a plurality of optically triggered assistant thyristors defined in the base layer and configured to supply current to the base layer of the primary thyristor in response to an optical signal;

wherein the optically triggered thyristor is configured to sustain at least 10 kV in reverse blocking mode; and

wherein the optically triggered thyristor has a positive temperature coefficient of forward voltage at a forward current density less than 100 A/cm 2 .

12. The optically triggered thyristor of claim 11 , wherein the primary thyristor comprises:

a semiconductor layer having a first conductivity type and a first doping concentration;

a carrier injection layer on the semiconductor layer, the carrier injection layer having the first conductivity type and a second doping concentration that is lower than the first doping concentration, wherein the carrier injection layer has a thickness greater than 1 micron;

a drift layer on the carrier injection layer, the drift layer having the second conductivity type;

a base layer having the first conductivity type on the drift layer; and

an anode region having the second conductivity type on the base layer.

13. The optically triggered thyristor of claim 12 , wherein the primary thyristor further comprises:

a buffer layer having the second conductivity type between the carrier injection layer and the drift layer, wherein the carrier injection layer and the buffer layer form a p-n junction;

wherein the carrier injection layer is thicker than the buffer layer.

14. The optically triggered thyristor of claim 11 , wherein a cross-over current density at which the primary thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is less than 75 A/cm 2 .

15. The optically triggered thyristor of claim 14 , wherein the cross-over current density at which the primary thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is between 50 A/cm 2 and 75 A/cm 2 .

16. An optically triggered silicon carbide thyristor, comprising:

a silicon carbide buffer layer, the first silicon carbide buffer layer having a first conductivity type;

a silicon carbide drift layer on the second buffer layer, the silicon carbide drift layer having a second conductivity type opposite the first conductivity type;

a silicon carbide base layer having the first conductivity type on the silicon carbide drift layer, wherein the silicon carbide base layer is divided into a main base layer and at least one assistant base layer that is isolated from the main base layer;

a first silicon carbide anode region having the second conductivity type on the main base layer;

a second silicon carbide anode region having the second conductivity type on the assistant base layer; and

a conductive interconnect that conductively connects the second anode region and the main base layer;

wherein a thickness and doping concentration of the silicon carbide buffer layer are selected to reduce minority carrier injection across a p-n junction with the silicon carbide buffer layer in response to an increase in operating temperature of the optically triggered thyristor, and

wherein a cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is less than 100 A/cm 2 .

17. The optically triggered silicon carbide thyristor of claim 16 , further comprising a silicon carbide layer having the first conductivity type, wherein the silicon carbide buffer layer is on the silicon carbide layer, and wherein a doping concentration of the silicon carbide layer is greater than the doping concentration of the silicon carbide buffer layer.

18. The optically triggered silicon carbide thyristor of claim 17 , further comprising a second silicon carbide buffer layer having the second conductivity type between the silicon carbide buffer layer and the silicon carbide drift layer.

19. The optically triggered silicon carbide thyristor of claim 16 , wherein the cross-over current density at which the thyristor shifts from a negative temperature coefficient of forward voltage to a positive temperature coefficient of forward voltage is less than 75 A/cm 2 .

Assignments (6)