Crystal growing systems and methods including a passive heater

1. A system for growing a crystal ingot from a melt, the system comprising:

a crucible assembly including a crucible and a weir separating an outer melt zone of the melt from an inner melt zone of the melt;

a first heater configured to supply thermal energy to the melt by conduction through the crucible;

a second heater configured to generate thermal radiation;

a passive heater configured to supply thermal energy to the outer melt zone by transferring thermal radiation generated by the second heater to the outer melt zone, the passive heater being oriented at an angle of between about 30 degrees and about 50 degrees with respect to a surface of the melt; and

a conical heat shield positioned radially inward from the passive heater, the conical heat shield angling downward toward a central opening for receiving the ingot.

2. The system of claim 1 , wherein the passive heater is configured to supply thermal energy to the outer melt zone by reflecting thermal radiation generated by the second heater towards the outer melt zone.

3. The system of claim 2 , wherein the passive heater is configured to supply thermal energy to the outer melt zone by emitting thermal radiation towards the outer melt zone in response to absorbing thermal radiation generated by the second heater.

4. The system of claim 1 , wherein a total amount of thermal energy is supplied to the outer melt zone by at least the first heater, the second heater, and the passive heater, the passive heater configured to supply at least about 50% of the total amount of thermal energy supplied to the outer melt zone.

5. The system of claim 1 , wherein the passive heater includes a heat reflective layer and an insulating layer, the heat reflective layer configured to reflect thermal radiation generated by the second heater towards the outer melt zone.

6. The system of claim 5 , wherein the reflective layer includes at least one of graphite and silicon carbide.

7. The system of claim 1 , wherein the passive heater is positioned above the outer melt zone.

8. The system of claim 1 , wherein the passive heater has a generally frustoconical shape.

9. The system of claim 1 , wherein the crucible includes a base and a sidewall, the first heater disposed proximate the base of the crucible and radially inward from the sidewall of the crucible, the second heater disposed radially outward from the sidewall of the crucible.

10. The system of claim 1 , wherein the passive heater is positioned in direct line-of-sight with the second heater and the outer melt zone.

11. The system of claim 1 , further comprising a feed system configured to feed solid feedstock material into the outer melt zone.

12. The system of claim 1 , wherein the second heater is configured to generate visible light radiation.

13. The system of claim 1 , wherein the second heater is configured to generate infrared radiation.

14. A system for growing a crystal ingot from a melt, the system comprising:

a crucible assembly including a crucible and a weir separating an outer melt zone of the melt from an inner melt zone of the melt;

a first heater configured to supply thermal energy to the melt by conduction through the crucible;

a second heater configured to generate thermal radiation;

a passive heater configured to supply thermal energy to the outer melt zone by transferring thermal radiation generated by the second heater to the outer melt zone, the passive heater having a generally frustoconical shape; and

a conical heat shield positioned radially inward from the passive heater, the conical heat shield angling downward toward a central opening for receiving the ingot.

15. The system of claim 14 , wherein the passive heater is configured to supply thermal energy to the outer melt zone by reflecting thermal radiation generated by the second heater towards the outer melt zone.

16. The system of claim 15 , wherein the passive heater is configured to supply thermal energy to the outer melt zone by emitting thermal radiation towards the outer melt zone in response to absorbing thermal radiation generated by the second heater.

17. The system of claim 14 , wherein a total amount of thermal energy is supplied to the outer melt zone by at least the first heater, the second heater, and the passive heater, the passive heater configured to supply at least about 50% of the total amount of thermal energy supplied to the outer melt zone.

18. The system of claim 14 , wherein the passive heater includes a heat reflective layer and an insulating layer, the heat reflective layer configured to reflect thermal radiation generated by the second heater towards the outer melt zone.

19. The system of claim 18 , wherein the reflective layer includes at least one of graphite and silicon carbide.

20. The system of claim 14 , wherein the passive heater is positioned above the outer melt zone.

21. The system of claim 14 , wherein the crucible includes a base and a sidewall, the first heater disposed proximate the base of the crucible and radially inward from the sidewall of the crucible, the second heater disposed radially outward from the sidewall of the crucible.

22. The system of claim 14 , wherein the passive heater is positioned in direct line-of-sight with the second heater and the outer melt zone.

23. The system of claim 14 , further comprising a feed system configured to feed solid feedstock material into the outer melt zone.

24. The system of claim 14 , wherein the second heater is configured to generate visible light radiation.

25. The system of claim 14 , wherein the second heater is configured to generate infrared radiation.