Low resistivity contact
Embodiments of a low resistivity contact to a semiconductor structure are disclosed. In one embodiment, a semiconductor structure includes a semiconductor layer, a semiconductor contact layer having a low bandgap on a surface of the semiconductor layer, and an electrode on a surface of the semiconductor contact layer opposite the semiconductor layer. The bandgap of the semiconductor contact layer is in a range of and including 0 to 0.2 electron-volts (eV), more preferably in a range of and including 0 to 0.1 eV, even more preferably in a range of and including 0 to 0.05 eV. Preferably, the semiconductor layer is p-type. In one particular embodiment, the semiconductor contact layer and the electrode form an ohmic contact to the p-type semiconductor layer and, as a result of the low bandgap of the semiconductor contact layer, the ohmic contact has a resistivity that is less than 1×10 −6 ohms·cm 2 .
1. A semiconductor structure comprising:
a semiconductor layer;
a semiconductor contact layer on a surface of the semiconductor layer, the semiconductor contact layer having a bandgap that is in a range of and including 0 to 0.1 electron-volts; and
a metallic electrode on a surface of the semiconductor contact layer opposite the semiconductor layer.
2. The semiconductor structure of claim 1 wherein the semiconductor layer is a p-type semiconductor layer.
3. The semiconductor structure of claim 2 wherein the semiconductor contact layer and the metallic electrode form an ohmic contact having a resistivity that is less than 1×10 −6 ohms·cm 2 .
4. The semiconductor structure of claim 2 wherein the bandgap of the semiconductor contact layer is in a range of and including 0 to 0.05 electron-volts.
5. The semiconductor structure of claim 1 comprising an additional layer between the semiconductor contact layer and the metallic electrode.
6. The semiconductor structure of claim 1 further comprising:
a second semiconductor contact layer on a second surface of the semiconductor layer opposite the semiconductor contact layer, the second semiconductor contact layer having a bandgap that is in the range of and including 0 to 0.2 electron-volts; and
a second metallic electrode on a surface of the second semiconductor contact layer opposite the semiconductor layer.
7. The semiconductor structure of claim 1 wherein the metallic electrode is directly on the surface of the semiconductor contact layer opposite the semiconductor layer.
8. A semiconductor structure comprising:
a semiconductor layer;
a p-type semiconductor contact layer on a surface of the semiconductor layer, the p-type semiconductor contact layer being formed of Pb x Sn 1-x Se, where 0≦x≦1, and having a bandgap that is in a range of and including electron-volts; and
a metallic electrode on a surface of the p-type semiconductor contact layer opposite the semiconductor layer.
9. The semiconductor structure of claim 8 wherein the bandgap of the p-type semiconductor contact layer is in a range of and including 0 to 0.1 electron-volts.
10. The semiconductor structure of claim 8 wherein the bandgap of the p-type semiconductor contact layer is in a range of and including 0 to 0.05 electron-volts.
11. The semiconductor structure of claim 8 wherein the p-type semiconductor contact layer is formed of Pb x Sn 1-x Se, where 0≦x≦1, with a mole fraction of Sn in a range of and including 0.08 to 0.46.
12. The semiconductor structure of claim 8 wherein the p-type semiconductor contact layer is formed of Pb x Sn 1-x Se, where 0≦x≦1, with a mole fraction of Sn in a range of and including 0.18 to 0.37.
13. The semiconductor structure of claim 8 wherein the p-type semiconductor contact layer is formed of Pb x Sn 1-x Se, where 0≦x≦1, with a mole fraction of Sn in a range of and including 0.23 to 0.32.
14. A semiconductor structure comprising:
a semiconductor layer;
a p-type semiconductor contact layer on a surface of the semiconductor layer, the p-type semiconductor contact layer being formed of Pb x Sn 1-x Te, where 0≦x≦1, and having a bandgap that is in a range of and including 0 0.2 electron-volts; and
a metallic electrode on a surface of the p-type semiconductor contact layer opposite the semiconductor layer.
15. The semiconductor structure of claim 14 wherein the bandgap of the p-type semiconductor contact layer is in a range of and including 0 to 0.1 electron-volts.
16. The semiconductor structure of claim 14 wherein the bandgap of the p-type semiconductor contact layer is in a range of and including 0 to 0.05 electron-volts.
17. The semiconductor structure of claim 14 wherein the p-type semiconductor contact layer is formed of Pb x Sn 1-x Te, where 0≦x≦1, with a mole fraction of Sn in a range of and including 0.21 to 0.95.
18. The semiconductor structure of claim 14 wherein the p-type semiconductor contact layer is formed of Pb x Sn 1-x Te, where 0≦x≦1, with a mole fraction of Sn in a range of and including 0.4 to 0.76.
19. The semiconductor structure of claim 14 wherein the p-type semiconductor contact layer is formed of Pb x Sn 1-x Te, where 0≦x≦1, with a mole fraction of Sn in a range of and including 0.49 to 0.67.
20. A semiconductor structure comprising:
a semiconductor layer comprising a p-type thermoelectric material formed in a Group IIa and IV-VI materials system;
a semiconductor contact layer on a surface of the semiconductor layer, the semiconductor contact layer being formed of a Group IIa and IV-VI material having a bandgap that is in a range of and including 0 to 0.2 electron-volts; and
a metallic electrode on a surface of the semiconductor contact layer opposite the semiconductor layer.
21. A semiconductor structure comprising:
a semiconductor layer comprising a p-type PbSe based thermoelectric material;
a semiconductor contact layer on a surface of the semiconductor layer, the semiconductor contact layer being formed of Pb y Sn 1-y Se, where 0≦y≦1, and having a bandgap that is in a range of and including 0 to 0.2 electron-volts; and
a metallic electrode on a surface of the semiconductor contact layer opposite the semiconductor layer.
22. The semiconductor structure of claim 21 wherein the p-type PbSe based thermoelectric material comprises at least one layer of PbSe and at least one layer of Pb x Sr 1-x Se, where 0≦x≦1.
23. A semiconductor structure comprising:
a semiconductor layer comprises comprising a p-type PbSe based thermoelectric material;
a semiconductor contact layer on a surface of the semiconductor layer, the semiconductor contact layer being formed of Pb x Sn 1-x Te, where 0≦x≦1, and having a bandgap that is in a range of and including 0 to 0.2 electron-volts; and
a metallic electrode on a surface of the semiconductor contact layer opposite the semiconductor layer.
24. The semiconductor structure of claim 23 wherein the p-type PbSe based thermoelectric material comprises at least one layer of PbSe and at least one layer of Pb x Sr 1-x Se, where 0≦x≦1.
25. A method of fabricating a semiconductor structure comprising:
providing a semiconductor layer;
providing a semiconductor contact layer on a surface of the semiconductor layer, the semiconductor contact layer having a bandgap that is in a range of and including 0 to 0.1 electron-volts; and
providing a metallic electrode on a surface of the semiconductor contact layer opposite the semiconductor layer.