Optically controlled silicon carbide and related wide-bandgap transistors and thyristors
View Patent ↗An optically active material is used to create power devices and circuits having significant performance advantages over conventional methods for affecting optical control of power electronics devices and circuits. A silicon-carbide optically active material is formed by compensating shallow donors with the boron related D-center. The resulting material can be n-type or p-type but it is distinguished from other materials by the ability to induce persistent photoconductivity in it when illuminated by electromagnetic radiation with a photon energy in excess of the threshold energy required to photoexcite electrons from the D-center to allowed states close to the conduction band edge, which varies from polytype to polytype.
1. A method of making a semiconductor device comprising:
forming a first layer of n-type SiC semiconductor material on an n-type conducting substrate;
forming an optically active, semi-insulating SiC region on the first layer of n-type SiC semiconductor material;
forming a second layer of n-type SiC semiconductor material on the optically active, semi-insulating SiC region;
selectively etching through the second layer of n-type SiC semiconductor material, the optically active, semi-insulating SiC region and the first layer of n-type SiC semiconductor material in a peripheral region of the device to form a mesa having sidewalls; and
depositing dielectric material on the sidewalls of the mesa.
2. The method of claim 1 , further comprising:
forming an ohmic contact on the surface of the second layer of n-type SiC semiconductor material opposite the optically active, semi-insulating SiC region;
forming an ohmic contact on the surface of the substrate opposite the first layer of n-type SiC semiconductor material.
3. The method of claim 1 , wherein forming the optically active, semi-insulating SiC region on the first layer of n-type SiC semiconductor material comprises doping the first layer of n-type SiC semiconductor material with boron such that boron-related D-center defects are formed in the first layer.
4. A method of making a semiconductor device comprising:
forming a first layer of n-type SiC semiconductor material on an n-type conducting substrate;
forming a second layer of n-type SiC semiconductor material on the first layer of n-type SiC semiconductor material;
forming a third layer of n-type SiC semiconductor material on the second layer of n-type SiC semiconductor material;
selectively etching through the third layer of n-type SiC semiconductor material to expose portions of the underlying second layer of n-type SiC semiconductor material thereby forming trenches;
selectively implanting boron in the exposed portions of the underlying second layer of n-type SiC semiconductor material at the bottom of the trenches to form optically active, semi-insulating SiC regions in the second layer of n-type SiC semiconductor material; and
depositing dielectric material in the trenches.
5. The method of claim 4 , further comprising:
depositing one or more metal layers on the third layer of n-type SiC semiconductor material and on the dielectric material in the trenches.
6. The method of claim 5 , further comprising forming openings in the one or more metal layers over the dielectric material.
7. The method of claim 6 , further comprising:
selectively etching through the third layer of n-type SiC semiconductor material, the second layer of n-type SiC semiconductor material and the first layer of n-type SiC semiconductor material in a peripheral region of the device to form a mesa having sidewalls; and
depositing dielectric material on the sidewalls of the mesa.
8. A method of making a semiconductor device comprising:
forming a drift layer of n-type SiC semiconductor material on an n-type conducting substrate;
forming a layer of p-type SiC semiconductor material on the drift layer, wherein the p-type layer is doped with a dopant other than boron;
implanting boron in the layer of p-type SiC semiconductor material;
selectively etching through the layer of p-type SiC semiconductor material to form first etched regions;
epitaxially growing a channel layer of n-type SiC semiconductor material in the etched regions and on the surface of the layer of p-type SiC semiconductor material adjacent the etched regions, wherein boron diffuses into the channel layer during epitaxial growth of the channel layer to form one or more optically active, semi-insulating SiC regions in the channel layer; and
epitaxially growing a source layer of n-type SiC semiconductor material on the channel layer.
9. The method of claim 8 , further comprising:
forming a source ohmic contact on the source layer; and
forming a drain ohmic contact on the substrate opposite the drift layer,
wherein the source ohmic contact is in electrical contact with the layer of p-type SiC semiconductor material.
10. The method of claim 9 , further comprising:
selectively etching through the source ohmic contact to form second etched regions.
11. The method of claim 10 , further comprising depositing dielectric material on the source layer in the second etched regions.
12. The method of claim 11 , further comprising selectively etching through the source layer to form third etched regions.
13. The method of claim 12 , further comprising depositing dielectric material on the channel layer in the third etched regions.
14. The method of claim 9 , further comprising:
selectively etching through the layer of p-type SiC semiconductor material and the drift layer in a peripheral region of the device to form a mesa having sidewalls; and
depositing dielectric material on the sidewalls of the mesa.