Phase change material layers

1. A phase change material layer, comprising:

germanium (Ge), antimony (Sb), tellurium (Te) and at least one impurity element,

wherein an atomic concentration of the at least one impurity element ranges from about 0<a≦about 0.25,

an atomic concentration of antimony (Sb) ranges from about 0.03<c≦ about 0.15; and

a crystallization rate of the phase change material within a crystallization temperature range of the phase change material is larger than crystallization rates of GeTe and Ge 2 Sb 2 Te 5 .

2. The phase change material layer of claim 1 , wherein the atomic concentration of antimony (Sb) ranges from about 0.07≦c≦ about 0.09.

3. The phase change material layer of claim 1 , wherein an atomic concentration of germanium (Ge) ranges from about 0.3≦b< about 0.55.

4. The phase change material layer of claim 3 , wherein the atomic concentration of the at least one impurity element ranges from about 0<a≦ about 0.2, and

the atomic concentration of germanium (Ge) ranges from about 0.35≦b< about 0.47.

5. The phase change material layer of claim 1 , wherein the at least one impurity element includes one of boron (B), carbon (C), nitrogen (N), oxygen (O), aluminum (Al), silicon (Si), phosphorus (P) and sulfur (S).

6. The phase change material layer of claim 3 , wherein the at least one impurity element includes bismuth (Bi).

7. The phase change material layer of claim 1 , wherein a 10 years operating temperature of the phase change material layer is above about 70° C.

8. The phase change material layer of claim 1 , wherein the phase change material layer includes a first impurity element and a second impurity element, the first and second impurity elements, respectively, being boron (B), carbon (C), nitrogen (N), oxygen (O), aluminum (Al), silicon (Si), phosphorus (P) and/or sulfur (S),

and a sum of amounts of the first and second impurity elements ranges from about 0<a1+a2≦ about 0.2.

9. A phase change material layer, comprising:

germanium (Ge), antimony (Sb), tellurium (Te) and at least one impurity element,

wherein a 10 years operating temperature of the phase change material layer is above about 70° C., and

the phase change material layer has a crystallization rate within a crystallization temperature range of the phase change material that is larger than crystallization rates of GeTe and Ge 2 Sb 2 Te 5 .

10. A phase change material layer comprising a quaternary compound,

wherein the quaternary compound includes GeSbTe doped with at least one of impurity elements,

and the composition of GeSbTe is located in an area of a phase diagram surrounded by,

a first composition line having an atomic concentration of antimony (Sb) of about 0.03;

a second composition line having an atomic concentration of antimony (Sb) of about 0.15;

a third composition line having an atomic concentration of germanium (Ge) of about 0.3; and

a fourth composition line having an atomic concentration of germanium (Ge) of about 0.55; and

wherein a crystallization rate of the phase change material within a crystallization temperature range of the phase change material is larger than crystallization rates of GeTe and Ge 2 Sb 2 Te 5 .

11. The phase change material layer of claim 10 , wherein the composition of GeSbTe is overlapped with a tie line between GeTe and Sb 2 Te 3 .

12. A phase change device, comprising:

a first electrode and a second electrode; and

a phase change material layer coupled to the first and second electrodes, the phase change material layer being configured to undergo a phase transition from one of an amorphous state and a crystalline state to another of the amorphous state and the crystalline state when a voltage is applied between the first electrode and the second electrode;

a crystallization rate of the phase change material layer within a crystallization temperature range of the phase change material layer being larger than crystallization rates of GeTe and Ge 2 Sb 2 Te 5 .

13. The phase change device of claim 12 , wherein the phase change material layer comprises a chalcogenide.

14. The phase change device of claim 13 , wherein the phase change material layer comprises germanium (Ge), antimony (Sb), tellurium (Te) and at least one impurity element.

15. The phase change device of claim 14 , wherein:

an atomic concentration of the at least one impurity element ranges from 0 to about 0.25, and

an atomic concentration of antimony (Sb) ranges from about 0.03 to about 0.15.

16. The phase change material device of claim 14 , wherein the at least one impurity element comprises at least one of bismuth (Bi), boron (B), carbon (C), nitrogen (N), oxygen (O), aluminum (Al), silicon (Si), phosphorus (P) and sulfur (S); and

the atomic concentration of the at least one impurity element ranges from 0 to about 0.2.

17. The phase change material device of claim 14 , wherein an atomic concentration of germanium (Ge) ranges from about 0.3 to about 0.55.

18. The phase change device of claim 12 , wherein the first electrode is provided on a structure including:

a substrate;

a word line disposed on the substrate;

an isolation layer pattern between portions of the word line and the substrate, wherein the portions of the word line and the substrate that include the isolation layer are field regions, and other portions are active regions;

a switching unit disposed on the word line;

an ohmic pattern disposed on the switching unit; and

a plug disposed on the ohmic pattern, wherein the first electrode is disposed on the plug.