High-resistivity silicon carbide substrate for semiconductor devices with high break down voltage
First Claim
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1. A semiconductor structure comprising:
- a silicon carbide single crystal substrate; and
a doped epitaxial layer of silicon carbide on said substrate;
said substrate comprising at least one compensated dopant having an electronic energy level far enough from an edge of the silicon carbide bandgap to avoid conductive behavior, while far enough from mid-gap towards the band edge to create a greater band offset between said substrate and said epitaxial layer than do mid-level states when said substrate is in contact with said silicon carbide epitaxial layer and when the net amount of said dopant present in said substrate is sufficient to pin the Fermi level of said substrate at said dopant'"'"'s electronic energy level; and
said silicon carbide substrate having a resistivity of at least 5000 ohms-centimeters at room temperature (298K).
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Abstract
A high-resistivity silicon carbide single crystal is disclosed that includes at least one compensated dopant having an electronic energy level far enough from an edge of the silicon carbide bandgap to avoid conductive behavior, while far enough from mid-gap towards the band edge to create a greater band offset than do mid-level states when the substrate is in contact with a doped silicon carbide epitaxial layer and when the net amount of the dopant present in the crystal is sufficient to pin the Fermi level at the dopant'"'"'s electronic energy level. The silicon carbide crystal has a resistivity of at least 5000 ohms-centimeters at room temperature.
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Citations
67 Claims
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1. A semiconductor structure comprising:
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a silicon carbide single crystal substrate; and
a doped epitaxial layer of silicon carbide on said substrate;
said substrate comprising at least one compensated dopant having an electronic energy level far enough from an edge of the silicon carbide bandgap to avoid conductive behavior, while far enough from mid-gap towards the band edge to create a greater band offset between said substrate and said epitaxial layer than do mid-level states when said substrate is in contact with said silicon carbide epitaxial layer and when the net amount of said dopant present in said substrate is sufficient to pin the Fermi level of said substrate at said dopant'"'"'s electronic energy level; and
said silicon carbide substrate having a resistivity of at least 5000 ohms-centimeters at room temperature (298K). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
the concentration of said boron being greater than the concentration of said scandium; and
the net concentration of said boron, said point defects and said scandium being sufficient to pin the Fermi level at the level of said scandium in the presence of said intrinsic nitrogen.
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5. A silicon carbide structure according to claim 4 wherein electrons from said nitrogen fill the energy level of said boron and partially fill the energy level of said scandium.
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6. A field-effect transistor that includes the semi-insulating silicon carbide substrate according to claim 5.
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7. A semiconductor structure according to claim 1 wherein:
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said doped epitaxial layer is p-type; and
said net dopant in said substrate is n-type.
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8. A semiconductor structure according to claim 1 wherein:
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said doped epitaxial layer is n-type; and
said net dopant in said substrate is p-type.
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9. A silicon carbide structure according to claim 1 wherein the polytype of the silicon carbide is selected from the group consisting of the 3C, 4H, 6H and 15R polytypes.
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10. A silicon carbide structure according to claim 1 having a resistivity of at least 10,000 ohms-centimeters at room temperature.
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11. A silicon carbide structure according to claim 1 having a resistivity of at least 50,000 ohms-centimeters at room temperature.
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12. A silicon carbide single crystal comprising:
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nitrogen; and
at least one acceptor element having an electronic energy level of between 0.3 and 1.4 eV relative to the valence band of mono-crystalline silicon carbide;
said at least one acceptor element being present in an amount that over compensates the nitrogen and pins the Fermi level of said silicon carbide substrate to the electronic energy level of said at least one acceptor element. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A silicon carbide single crystal comprising;
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an amount of electrically active nitrogen;
an amount of electrically active point defects that act as acceptors; and
an amount at least one acceptor element having an electronic energy level of between 0.3 and 1.4 eV relative to the valence band of mono-crystalline silicon carbide;
wherein the combined amount of said acceptor element and said point defects is greater than said amount of electrically active nitrogen and pins the Fermi level of said silicon carbide single crystal to the electronic energy level of said at least one acceptor element. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31)
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32. A bulk single crystal of silicon carbide comprising:
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non-intentionally introduced nitrogen;
scandium; and
boron; and
whereinthe concentration of nitrogen is greater than the concentration of scandium; and
the concentration of boron is sufficient for the sum concentration of boron and scandium to overcompensate the nitrogen, and pin the Fermi level of said silicon carbide to the level of said scandium. - View Dependent Claims (33, 34, 35, 36, 37, 38)
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39. A bulk single crystal of silicon carbide comprising:
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nitrogen in a concentration of between about 5E15 and 3E16 cm−
3;
boron in a concentration of 1E16 cm−
3;
scandium in a concentration of between about 1E15 and 2E16 cm−
3;
point defects in a concentration of between about 1E14 and 3E16 cm−
3; and
a resistivity of at least 5000 Ω
-cm at room temperature.- View Dependent Claims (40, 41, 42, 43, 44, 45)
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46. A silicon carbide single crystal comprising;
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electrically active nitrogen;
electrically active point defects that act as acceptors;
a first acceptor element having an electronic energy level of between 0.3 and 1.4 eV relative to the valence band of mono-crystalline silicon carbide; and
a second acceptor element having an electronic energy level of between 0.3 and 1.4 eV relative to the valence band of mono-crystalline silicon carbide;
said energy level of said first acceptor element being deeper than the energy level of said second acceptor element;
the concentration of said second acceptor element being greater than the amount of said first acceptor element; and
the combined amount of said acceptor elements and said point defects being greater than said amount of electrically active nitrogen and pins the Fermi level of said silicon carbide substrate to the electronic energy level of said first acceptor element. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54)
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55. A semiconductor structure comprising:
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a silicon carbide single crystal substrate; and
a doped region of silicon carbide adjacent said substrate;
said substrate comprising at least one compensated dopant having an electronic energy level far enough from an edge of the silicon carbide bandgap to avoid conductive behavior, while far enough from mid-gap towards the band edge to create a greater band offset between said substrate and said doped region than do mid-level states when said substrate is in contact with said doped region and when the net amount of said dopant present in said substrate is sufficient to pin the Fermi level of said substrate at said dopant'"'"'s electronic energy level; and
said silicon carbide substrate having a resistivity of at least 5000 ohms-centimeters at room temperature (298K) . - View Dependent Claims (56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67)
the concentration of said boron being greater than the concentration of said scandium; and
the net concentration of said boron, said point defects and said scandium being sufficient to pin the Fermi level at the level of said scandium in the presence of said intrinsic nitrogen.
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59. A silicon carbide structure according to claim 58 wherein electrons from said nitrogen fill the energy level of said boron and partially fill the energy level of said scandium.
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60. A field-effect transistor that includes the semi-insulating silicon carbide substrate according to claim 59.
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61. A semiconductor structure according to claim 55 wherein:
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said adjacent doped region is p-type; and
said net dopant in said substrate is n-type.
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62. A semiconductor structure according to claim 55 wherein:
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said adjacent doped region is n-type; and
said net dopant in said substrate is p-type.
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63. A silicon carbide structure according to claim 55 wherein the polytype of the silicon carbide is selected from the group consisting of the 3C, 4H, 6H and 15R polytypes.
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64. A silicon carbide structure according to claim 55 having a resistivity of at least 10,000 ohms-centimeters at room temperature.
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65. A silicon carbide structure according to claim 55 having a resistivity of at least 50,000 ohms-centimeters at room temperature.
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66. A silicon carbide structure according to claim 55 wherein said adjacent doped region is a dopant-implanted region.
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67. A silicon carbide structure according to claim 55 wherein said adjacent doped region is a dopant-diffused region.
Specification