Optoelectronic device containing at least one active device layer having a wurtzite crystal structure, and methods of making same
Optoelectronic devices, such as light-emitting diodes, laser diodes, image sensors, optical detectors, etc., made by depositing (growing) one or more epitaxial semiconductor layers on a monocrystalline lamellar/layered substrate so that each layer has a wurtzite crystal structure. In some embodiments, the layers are deposited and then one or more lamellas of the starting substrate are removed from the rest of the substrate. In one subset of such embodiments, the removed lamella(s) is/are partially or entirely removed. In other embodiments, one or more lamellas of the starting substrate are removed prior to depositing the one or more wurtzite-crystal-structure-containing layer(s).
1. A method of fabricating a light-generating optoelectronic device, the method comprising:
providing a starting substrate, wherein the starting substrate has a naturally lamellar single-crystal structure and is selected to induce a wurtzite crystal structure in a coating layer applied to the starting substrate, wherein the coating layer comprises a II-VI semiconductor;
forming a light-generating optoelectronic structure, wherein said forming the light-generating optoelectronic structure includes forming the coating layer as an epitaxial layer on the starting substrate so that the coating layer has the wurtzite crystal structure, wherein the coating layer has a base composition of a II-VI semiconductor base composition or a I-VI semiconductor base composition;
cleaving the starting substrate so as to provide a sliver of the starting substrate on which the coating layer is formed; and
providing a pair of electrodes in electrical communication with the light-generating optoelectronic structure so that when a current is supplied across the light-generating optoelectronic structure via the pair of electrodes the light-generating optoelectronic structure emits light.
2. A method according to claim 1 , wherein said providing a starting substrate includes providing a substrate having a base selected from the group consisting of GaTe, WS 2 , ZnIn 2 S 4 , SnS 2 , Bi 2 Se 3 , Bi 2 Te 3 , GeSe, and PbI 2 .
3. A method according to claim 2 , wherein said forming a coating layer as an epitaxial layer includes forming a coating layer wherein the coating layer has a II-VI semiconductor base composition selected from a group consisting of ZnS, ZnSSe, ZnSe, CdS, CdSSe, HgS, CdSe, ZnTe, HgSe, CdTe, and HgTe.
4. A method according to claim 3 , wherein:
said providing a starting substrate includes providing a substrate having a base selected from the group consisting of WS 2 and ZnIn 2 S 4 ; and
said forming a coating layer as an epitaxial layer includes forming a coating layer wherein the coating layer has a II-VI semiconductor base composition selected from a group consisting of ZnS, ZnSSe, ZnSe.
5. A method according to claim 3 , wherein:
said providing a starting substrate includes providing a substrate having a base selected from the group consisting of SnS 2 , Bi 2 Se 3 , and GaTe; and
said forming a coating layer as an epitaxial layer includes forming a coating layer wherein the coating layer has a II-VI semiconductor base composition selected from a group consisting of ZnSe, ZnSSe, CdS, CdSSe, and HgS.
6. A method according to claim 3 , wherein:
said providing a starting substrate includes providing a substrate having a base selected from a group consisting of Bi 2 Te 3 and GeSe; and
said forming a coating layer as an epitaxial layer includes forming a coating layer wherein the coating layer has a II-VI semiconductor base composition selected from a group consisting of CdSe, CdSSe, ZnTe, and HgSe.
7. A method according to claim 3 , wherein:
said providing a starting substrate includes providing a substrate having a base of PbI 2 ; and
said forming a coating layer as an epitaxial layer includes forming a coating layer wherein the coating layer has a II-VI semiconductor base composition selected from a group consisting of CdTe and HgTe.
8. A method according to claim 1 , wherein:
said providing a starting substrate includes providing a substrate having a base of GaSe; and
said forming a coating layer as an epitaxial layer includes forming a coating layer wherein the coating layer has a II-VI semiconductor base composition selected from a group consisting of ZnS, ZnSSe, and ZnSe.
9. A method according to claim 1 , wherein:
said providing a starting substrate includes providing a substrate having a base of GaSe; and
said forming a light-generating optoelectronic structure includes:
forming, on the starting substrate, a first ZnS coating layer having a wurtzite crystal structure and a doping of a first type;
forming, over the first ZnS coating layer, a CdSe quantum confining layer having a wurtzite crystal structure; and
forming, over the CdSe quantum confining layer, a second ZnS coating layer having a wurtzite crystal structure and a doping of a second doping type opposite the first doping type.
10. A method according to claim 1 , wherein:
said providing a starting substrate includes providing a substrate having a base of GaSe; and
said forming a light-generating optoelectronic structure includes:
forming, on the starting substrate, a first ZnS coating layer having a wurtzite crystal structure and a doping of a first type;
forming, over the first ZnS coating layer, a CdS quantum confining layer having a wurtzite crystal structure; and
forming, over the CdS quantum confining layer, a second ZnS coating layer having a wurtzite crystal structure and a doping of a second doping type opposite the first doping type.
11. A method according to claim 1 , wherein:
said providing a starting substrate includes providing a substrate having a base of GaSe; and
said forming a light-generating optoelectronic structure includes:
forming, on the starting substrate, a first ZnS coating layer having a wurtzite crystal structure and a doping of a first type;
forming, over the first ZnS coating layer, a HgS quantum confining layer having a wurtzite crystal structure; and
forming, over the HgS quantum confining layer, a second ZnS coating layer having a wurtzite crystal structure and a doping of a second doping type opposite the first doping type.
12. A method according to claim 1 , wherein:
said providing a starting substrate includes providing a substrate having a base of GaSe; and
said forming a light-generating optoelectronic structure includes:
forming, on the starting substrate, a first ZnS coating layer having a wurtzite crystal structure and a doping of a first type;
forming, over the first ZnS coating layer, a Cu x S quantum confining layer having a wurtzite crystal structure; and
forming, over the Cu x S quantum confining layer, a second ZnS coating layer having a wurtzite crystal structure and a doping of a second doping type opposite the first doping type.
13. A method according to claim 1 , wherein:
said providing a starting substrate includes providing a substrate having a base selected from a group consisting of Bi 2 Te 3 and Bi 2 Se 3 ; and
said forming a light-generating optoelectronic structure includes:
forming, on the starting substrate, a CdS coating layer having a wurtzite crystal structure and a doping of a first type;
forming, over the CdS coating layer, a quantum confining layer having a wurtzite crystal structure and a base composition selected from the group consisting of CdSe and HgS; and
forming, over the quantum confining layer, a ZnTe coating layer having a wurtzite crystal structure and a doping of a second doping type opposite the first doping type.
14. A method according to claim 1 , wherein:
said providing a starting substrate includes providing a substrate having a base of GaSe; and
said forming a light-generating optoelectronic structure includes:
forming, on the starting substrate, a ZnSe coating layer having a wurtzite crystal structure and a doping of a first type;
forming, over the ZnSe coating layer, a Cu x S quantum confining layer having a wurtzite crystal structure; and
forming, over the Cu x S quantum confining layer, a Cu x S coating layer having a wurtzite crystal structure and a doping of a second doping type opposite the first doping type.
15. A method according to claim 1 , further comprising finishing fabricating the surface-emitting light-generating optoelectronic device so that at least a portion of the sliver of the starting substrate remains intact.
16. A method according to claim 1 , further comprising removing the sliver of the starting substrate prior to finishing fabricating the surface-emitting light-generating optoelectronic device.
17. A method according to claim 1 , wherein said providing a pair of electrodes includes providing the pair of electrodes on opposite sides of the coating layer.
18. A method according to claim 1 , wherein said providing a pair of electrodes includes providing the pair of electrodes on the same side of the coating layer.
19. A method according to claim 1 , wherein said cleaving the starting substrate includes cleaving the starting substrate after said forming the coating layer.
20. A method according to claim 1 , wherein said cleaving the starting substrate includes cleaving the starting substrate before forming the coating layer.
21. A method according to claim 1 , wherein said forming a coating layer as an epitaxial layer includes forming a coating layer wherein the coating layer has a I-VI semiconductor base composition.
22. A method according to claim 21 , wherein said forming a coating layer having a I-VI semiconductor base composition includes forming a coating layer having a copper sulfide base composition.