Switching device having bi-directional drive characteristics and method of operating same
Disclosed is a bi-directional two-terminal phase-change memory device using a tunneling thin film and a method of operating the same. According to an one embodiment, a phase-change memory device comprises: a first electrode; a second electrode; and a phase-change memory cell interposed between the first electrode and the second electrode, wherein the phase-change memory cell comprises: a P-type intermediate layer used as a data storage as a crystal state changes due to a voltage applied through the first electrode and the second electrode; an upper layer and a lower layer formed using an N-type semiconductor material at both ends of the intermediate layer; and at least one tunneling thin film disposed on at least one area from among an area between the upper layer and the intermediate layer or an area between the lower layer and the intermediate layer, so as to reduce a leakage current in the intermediate layer or prevent intermixing between a P-type dopant and an N-type dopant.
1. A phase-change memory device comprising:
a first electrode;
a second electrode; and
a phase-change memory cell interposed between the first electrode and the second electrode,
wherein the phase-change memory cell comprises:
a P-type intermediate layer used as data storage as a crystal state changes due to a voltage applied through the first electrode and the second electrode;
an upper layer and a lower layer formed using an N-type semiconductor material at both ends of the intermediate layer; and
at least one tunneling thin film arranged in at least one area from among an area between the upper layer and the intermediate layer and an area between the lower layer and the intermediate layer, the at least one tunneling thin film being configured to reduce a leakage current in the intermediate layer or prevent intermixing between a P-type dopant and an N-type dopant.
2. The phase-change memory device of claim 1 , wherein the at least one tunneling thin film is formed using a material to have a thickness to reduce the leakage current or prevent the intermixing between the P-type dopant and the N-type dopant and simultaneously allow a flow of a tunneling current.
3. The phase-change memory device of claim 1 , wherein the phase-change memory cell is formed to have an NPN structure to selectively switch a voltage applied from the first electrode and the second electrode to the intermediate layer.
4. The phase-change memory device of claim 1 , wherein the phase-change memory cell is configured to implement a bi-directional current drive by forming bi-directional PN diodes using an NPN structure.
5. The phase-change memory device of claim 1 , wherein the phase-change memory cell is configured to perform a write operation of changing a crystal state of the intermediate layer as the intermediate layer is depleted due to an NP reverse bias in an NPN structure and a tunneling current flows.
6. The phase-change memory device of claim 1 , wherein the phase-change memory cell is configured to perform a read operation of reading a voltage difference caused by a variation in a depletion turn-on voltage due to a change of a crystal state of the intermediate layer, or
perform a read operation of reading a read current according to a variation in a resistance of the intermediate layer.
7. The phase-change memory device of claim 1 , wherein the intermediate layer is formed using a phase-change material containing a transition metal to have reverse phase-change characteristics.
8. A phase-change memory device comprising:
a first electrode;
a second electrode;
a P-type phase-change layer interposed between the first electrode and the second electrode, the P-type phase-change layer being used as a data storage as a crystal state changes due to a voltage applied through the first electrode and the second electrode; and
an N-type semiconductor layer arranged on the P-type phase-change layer,
wherein the P-type phase-change layer and the N-type semiconductor layer form a PN diode, and
the P-type phase-change layer forms a Schottky diode at a contact interface with the second electrode.
9. The phase-change memory device of claim 8 , wherein the phase-change memory device is configured to implement bi-directional current drive using the PN diode and the Schottky diode.
10. The phase-change memory device of claim 8 , wherein the P-type phase-change layer is formed by doping nitrogen into a phase-change material containing a transition metal to form a Schottky diode having stable Schottky characteristics at the contact interface with the second electrode.
11. A phase-change memory device comprising:
a first electrode;
a second electrode; and
a phase-change memory cell interposed between the first electrode and the second electrode,
wherein the phase-change memory cell comprises:
a first N-type semiconductor material layer;
a second N-type semiconductor material layer;
a P-type intermediate layer between the first and second N-type semiconductor material layers and used as data storage as a crystal state changes due to a voltage applied through the first electrode and the second electrode;
a first tunneling thin film arranged between the first N-type semiconductor material layer and the P-type intermediate layer, the first tunneling thin film configured to reduce a leakage current in the intermediate layer or prevent intermixing between a N-type dopant present in the first N-type semiconductor material layer and a P-type dopant present in the P-type intermediate layer.
12. The phase-change memory device of claim 11 , further comprising:
a second tunneling thin film arranged between the second N-type semiconductor material layer and the P-type intermediate layer.
13. The phase-change memory device of claim 11 , wherein the phase-change memory cell is formed to have an NPN structure to selectively switch a voltage applied from the first electrode and the second electrode to the P-type intermediate layer.
14. The phase-change memory device of claim 11 , wherein the phase-change memory cell is configured to implement a bi-directional current drive by forming bi-directional PN diodes using an NPN structure.
15. The phase-change memory device of claim 11 , wherein the phase-change memory cell is configured to perform a write operation of changing a crystal state of the P-type intermediate layer as the P-type intermediate layer is depleted due to an NP reverse bias in an NPN structure and a tunneling current flows.
16. The phase-change memory device of claim 11 , wherein the P-type intermediate layer comprises phase-change material containing a transition metal and has reverse phase-change characteristics.