Nonvolatile memory cell comprising a diode and a resistance-switching material

1. A method for programming a memory cell in a memory array, wherein the memory cell comprises a resistivity-switching layer of a metal oxide or nitride compound, the metal oxide or nitride compound including exactly one metal, and a diode in series with the resistivity-switching layer, the method comprising:

programming the memory cell by changing the resistivity-switching layer from a first resistivity state to a second programmed resistivity state,

wherein the second programmed resistivity state stores a data state of the memory cell.

2. A method for programming a memory cell in a memory array, wherein the memory cell comprises a resistivity-switching layer of a metal oxide or nitride compound, the metal oxide or nitride compound including exactly one metal, the method comprising:

programming the memory cell by changing the resistivity-switching layer from a first resistivity state to a second programmed resistivity state,

wherein the second programmed resistivity state stores a data state of the memory cell, and

wherein the memory array comprises circuitry to program and read the memory cell, and wherein the circuitry is adapted to program the memory cell no more than one time, and wherein the memory array is a one-time-programmable array.

3. The method of claim 2 , wherein the circuitry is adapted to program the memory cell to one of two possible data states.

4. The method of claim 2 , wherein the circuitry is adapted to program the memory cell to one of more than two possible data states.

5. The method of claim 2 , wherein the circuitry is adapted to program the memory cell to one of three or four possible data states.

6. The method of claim 2 , wherein programming the memory cell comprises applying a first programming pulse.

7. The method of claim 6 , further comprising reading the memory cell after applying the first programming pulse.

8. The method of claim 7 , further comprising applying a second programming pulse if the second programmed resistivity state has not been achieved.

9. The method of claim 1 , wherein the metal oxide or nitride compound is selected from the group consisting of Ni x O y , Nb x O y , Ti x O y , Hf x O y , Al x O y , Mg x O y , Co x O y , Cr x O y , V x O y , Zn x O y , Zr x O y , B x N y , and Al x N y .

10. The method of claim 1 , wherein the diode comprises a P-I-N diode.

11. The method of claim 1 , wherein the diode comprises silicon, germanium, or an alloy of silicon or germanium.

12. The method of claim 11 , wherein the silicon, germanium, or alloy of silicon or germanium is polycrystalline.

13. The method of claim 1 , wherein the memory array comprises circuitry to program and read the memory cell, and wherein the circuitry is adapted to program the memory cell to one of more than two possible data states.

14. The method of claim 13 , wherein the circuitry is adapted to program the memory cell to one of three or four possible data states.

15. The method of claim 1 , wherein the memory array is a rewriteable memory array.

16. A method for programming and sensing a memory cell in a memory array, wherein the memory cell comprises a resistivity-switching layer of a metal oxide or nitride compound, the metal oxide or nitride compound including exactly one metal, and a diode comprising polycrystalline semiconductor material, the resistivity-switching layer and the diode arranged electrically in series, the method comprising:

i) applying a first programming pulse to the memory cell wherein the first programming pulse:

a) detectably changes a first resistivity state of the resistivity-switching layer; or

b) detectably changes a second resistivity state of the polycrystalline semiconductor material, or

c) detectably changes the first resistivity state of the resistivity-switching layer and detectably changes the second resistivity state of the polycrystalline semiconductor material; and

ii) reading the memory cell, wherein the first resistivity state of the resistivity switching layer serves to store data and the second resistivity state of the polycrystalline semiconductor material serves to store data.

17. The method of claim 16 , wherein the memory cell is adapted to store one of three or four data states.

18. The method of claim 16 , wherein the polycrystalline semiconductor material is polysilicon.

19. The method of claim 16 , wherein the diode is a junction diode.

20. The method of claim 16 , wherein the metal oxide or nitride compound is selected from the group consisting of Ni x O y , Nb x O y , Ti x O y , Hf x O y , Al x O y , Mg x O y , Co x O y , Cr x O y , V x O y , Zn x O y , Zr x O y , B x N y , and Al x N y .

21. The method of claim 20 , wherein the metal oxide or nitride compound is selected from the group consisting of NiO, Nb 2 O 5 , TiO 2 , HfO 2 , Al 2 O 3 , MgO, CoO, CrO 2 , VO, ZnO, ZrO, BN, and AlN.

22. A method for programming a memory cell in a memory array, wherein the memory cell comprises a resistivity-switching layer of a metal oxide or nitride compound, the metal oxide or nitride compound including exactly one metal, and circuitry to program and read the memory cell, the method comprising:

programming the memory cell by changing the resistivity-switching layer from a first resistivity state to a second programmed resistivity state,

wherein the second programmed resistivity state stores a data state of the memory cell, and

the circuitry is adapted to program the memory cell to one of more than two possible data states.

23. The method of claim 22 , wherein the circuitry is adapted to program the memory cell to one of three or four possible data states.

24. The method of claim 22 , wherein the memory array is a rewriteable memory array.