1. Neutron Transmutation Doping Conceptual Design Dr. Mosa Othman Silicon doping facility manger Egyptian Second Research Raector (ETRR-2) Atomic Energy Authority Mosa_osman@yahoo.com 00201144420980020111882589

2. Charge Carrier in Semiconductors At zero Kelvin temperature semiconductors behave as insulators. At zero Kelvin temperature semiconductors behave as insulators. at higher temperatures some of the electrons from the top of completely filled valence band (outer shell) can make a transition across the energy gap and occupy state in the bottom of the conduction As a result, electrons and holes are created. at higher temperatures some of the electrons from the top of completely filled valence band (outer shell) can make a transition across the energy gap and occupy state in the bottom of the conduction As a result, electrons and holes are created. These electrons and holes are referred to as charge carriers.

3. Intrinsic silicon conduction

4. Intrinsic Semiconductors A semiconductor whose electrical conductivity dominated by the thermally generated EHPs is called intrinsic semiconductor (undoped semiconductors). n = p = ni n = p = ni gi = ri gi = ri Both rates are temperature dependent. Conduction by holes differs from conduction by electrons.

5. Extrinsic Semiconductors: Charge carriers can be introduced in semiconductors by introducing impurities into the lattice. This method termed doping (addition of controlled amount of impurities into the semiconductor lattice). Impurities are called dopants. Dopants are either extra electrons (donors) or extra holes (acceptors). Impurities are called dopants. Dopants are either extra electrons (donors) or extra holes (acceptors). If the excess carriers are electrons, the doped semiconductor is called negative type (n-type). Conversely, if the excess carriers are holes the doped semiconductor is called positive type (p-type). If the excess carriers are electrons, the doped semiconductor is called negative type (n-type). Conversely, if the excess carriers are holes the doped semiconductor is called positive type (p-type).

6. N-type and p-type

7. Mobility: the mobility of hole is only about the half of the mobility of electron. The mobility is the velocity per unit applied electric field. mobility measures the ease of carrier motion through a semiconductor.

8. General requirements for NTD Temperature of silicon ingot during irradiation < 180 C Less than 100 C the diffusion of the impurities and defects are minimum

9. NTD utilization power devices, - high-class devices - standard devices. discrete device The basic advantages of NTD silicon in comparison with conventionally doped material, is the better distribution of phosphorus in the crystal.

10. Irradiation Rigs

11. Horizontal rig

12. main reactors used in silicon doping

13. Radiation Damage in Silicon simple point defects to large disordered regions, such as rod-like defects (10mm long and 200 A0 diameter). The fast neutron the head-on collision of a 1 MeV neutron with the silicon atom will knock out about 200 silicon atoms from their lattice sites The fast neutron the head-on collision of a 1 MeV neutron with the silicon atom will knock out about 200 silicon atoms from their lattice sites Concentration of these defects varies depending on the fast neutron flux to thermal ratio and Ingot temperature during irradiation. semiconductor parameters such as mobility, resistivity, and minority carrier lifetime are severely degraded.

14. Isothermal Annealing of Silicon Previous experiments have demonstrated that annealing for 30 minute at 750 0C is sufficient to obtain the anticipated carrier concentration and mobility in NTD float zone silicon (FZ) over wide range of neutron flounce

15. Quality of Doped Silicon Large Diameter For 6 inches (152 mm) diameter ingots that are irradiated in a light water moderated research reactor, the radial resistivity gradient (RRG) is too large even when they rotated through the irradiation process. The 6 inches ingots, which currently make up more than 10 % of the market, are only irradiated in heavy water moderated reactors or those that can provide a similar neutron spectrum for irradiating silicon. The 6 inches ingots, which currently make up more than 10 % of the market, are only irradiated in heavy water moderated reactors or those that can provide a similar neutron spectrum for irradiating silicon.

16. Power devices switching time

17. Resistivity Ranges for Electrical Components

18. Neutron transmutation doping facility design

19. Rig design

20. Neutronic design

21. Thermal design

22. New design old design

23. Axial thermal neutron flux profile in position (1)

24. Axial thermal neutron flux profile in position (2)

25. Irradiation method (1)

26. Method (2)

27. spacer design results

29. Radial resistivity measurement

30. Maximum percentage variation

31. Resistivity measurements

32. Axial resistivity variation due to neutron flux shape

33. Results of New Design Verification:

34. Axial Resistivity Variation

35. Radial resistivity variation

36. silicon ingot thermal characterization during irradiation

37. T max. 500mm, 6 ”

38. Max. energy rate 500mm, 6 ”

39. Temperature gradient in 500 mm ingot and 6 inches diameter Temperature gradient in 500 mm ingot and 6 inches diameter

40. Maximum temperature in the silicon, water gap and aluminum container

41. temperature calculation in 400mm ingot length and 6 inches diameter

42. Maximum temperature in 400 mm ingot and 6 inches diameter

43. Maximum energy rate in 400 mm ingot

44. temperature calculation for 250 mm ingot length and 6 ” diameter

45. Maximum energy rate in 250 mm ingot and 6 ” diameter

46. Temperature gradient in 250 mm ingot length and 6 ” diameter

47. Calculation of temperature in five inches ingot (new design)

51. Max. temp. 280mm and 5 inches

54. 400 mm and 5 inches

55. Max. temp. and energy

56. 500 mm ingot – 5 inches

59. Temperature distribution using (FEHT)

60. MEASUREDE TEMP.

61. CALCULATED TEPM. (FEHT)

62. Minority carrier life time samples

63. minority carrier life time samples

64. Old design minority carrier life time 7.66 micro-sec (270 minute annealing)

65. Old design minority carrier life time 4.66 micro-sec (270 minute annealing)

66. New design minority carrier life time 138 micro-sec (60 minute annealing)

68. Resistivity measuring in-line 4-point probe

69. Measuring minority carrier life time

70. Container fabrication and handling tools modification

72. Handling tool modification

73. New container