Semiconductor material having tunable permittivity and tunable thermal conductivity
A layered structure for semiconductor application is described herein. The layered structure includes a starting material and a fully depleted porous layer formed over the starting material with high resistivity. In some embodiments, the layered structure further includes epitaxial layer grown over the fully depleted porous layer. Additionally, a process of making the layered structure including forming the fully depleted porous layer and epitaxial layer grown over the porous layer is described herein.
1. A layered structure comprising:
a starting material layer; and
a fully depleted porous layer over the starting material layer,
wherein a first band gap of the fully depleted porous layer is greater than a second band gap of the starting material layer and the fully depleted porous layer is elementally identical to the starting material layer,
wherein the fully depleted porous layer comprises a first porosity in a first region and a second porosity in a second region, and
wherein the first and second regions are adjacent to each other in a horizontal direction.
2. The layered structure of claim 1 , wherein the fully depleted porous layer is between 10-20 μm thick with resistivity greater than 10000 ohm-cm.
3. The layered structure of claim 1 , wherein the starting material layer comprises silicon.
4. The layered structure of claim 1 , wherein the starting material layer comprises a material having resistivity in a range of 0.1 to 10 ohm-cm.
5. The layered structure of claim 1 , wherein the starting material layer comprises a plurality of layers stacked vertically, wherein a resistivity of the plurality of layers of the starting material layer varies.
6. The layered structure of claim 1 , wherein the starting material layer is a silicon substrate with a <111> or <100> crystal orientation.
7. The layered structure of claim 1 , wherein the fully depleted porous layer is lattice matched to the starting material layer.
8. The layered structure of claim 1 , wherein the first region of the fully depleted porous layer comprises a plurality of sublayers stacked vertically, wherein a porosity of the plurality of sublayers is graded with a sublayer with a low porosity at a surface of the first region of the fully depleted porous layer, and a sublayer with a high porosity at an interface of the first region of the fully depleted porous layer and the starting material layer.
9. The layered structure of claim 1 , wherein the first region of the fully depleted porous layer comprises a plurality of sublayers stacked vertically, wherein a porosity of the plurality of sublayers is graded with a sublayer with a high porosity at a surface of the first region of the fully depleted porous layer, and a sublayer with a low porosity at an interface of the first region of the fully depleted porous layer and the starting material layer.
10. The layered structure of claim 1 , wherein the first region of the fully depleted porous layer comprises periodically alternating vertical sublayers of the first porosity and a third porosity.
11. The layered structure of claim 10 , wherein the first porosity is a high porosity, and the third porosity is a low porosity.
12. The layered structure of claim 10 , wherein the periodically alternating vertical sublayers of the first porosity and the third porosity form an acoustic reflector.
13. The layered structure of claim 10 , wherein the periodically alternating vertical sublayers of the first porosity and the third porosity form a coherent phonon structure.
14. The layered structure of claim 1 , wherein thermal conductivity of the layered structure is at least equal to 3 W/mK.
15. The layered structure of claim 1 , wherein permittivity of the layered structure is in a range of approximately 2 to 4 farads per meter.
16. A layered structure comprising:
a starting material layer;
a fully depleted porous layer over the starting material layer, wherein a first band gap of the fully depleted porous layer is greater than a second band gap of the starting material layer and the fully depleted porous layer is elementally identical to the starting material layer; and
an epitaxial layer grown over the fully depleted porous layer,
wherein the fully depleted porous layer comprises a first porosity in a first region and a second porosity in a second region, and
wherein the first and second regions are adjacent to each other in a horizontal direction.
17. The layered structure of claim 16 , wherein the epitaxial layer is a silicon semiconductor layer.
18. The layered structure of claim 16 , wherein the epitaxial layer is selected from the group consisting of a InP layer, a cREO layer, a Mo layer, a AlGaInN layer, a RE-III-N layer and a metal layer.
19. The layered structure of claim 16 , wherein the layered structure is a layer of an RF switch structure.
20. The layered structure of claim 16 , wherein the layered structure is a layer of an integrated passive device.
21. The layered structure of claim 16 , wherein the layered structure is a layer in an RF filter.
22. The layered structure of claim 16 , wherein the starting material layer comprises a first region having a first resistivity and a second region having a second resistivity.
23. The layered structure of claim 22 , wherein:
the fully depleted porous layer is formed over the first region; and
the layered structure further comprises a non-fully depleted porous layer formed over the second region.
24. The layered structure of claim 16 , wherein the starting material layer is a silicon substrate with a <111> or <100> crystal orientation.
25. A method of forming a layered structure, the method comprising:
forming a fully depleted porous layer from a starting material,
wherein a first band gap of the fully depleted porous layer is greater than a second band gap of the starting material and the fully depleted porous layer is elementally identical to the starting material, and
wherein the fully depleted porous layer comprises a first porosity in a first region and a second porosity in a second region, and
wherein the first and second regions are adjacent to each other in a horizontal direction.
26. The method of claim 25 , wherein the starting material is a p-type, boron doped substrate having a resistivity in the range of 0.1 to 10 ohm-cm.
27. The method of claim 25 , further comprising:
growing an epitaxial layer over the fully depleted porous layer.
28. The method of claim 25 , wherein the starting material is a silicon substrate with a <111> or <100> crystal orientation.