Ultraviolet light emitting AlGaN composition and ultraviolet light emitting device containing same
An AlGaN composition is provided comprising a group III-Nitride active region layer, for use in an active region of a UV light emitting device, wherein light-generation occurs through radiative recombination of carriers in nanometer scale size, compositionally inhomogeneous regions having band-gap energy less than the surrounding material. Further, a semiconductor UV light emitting device having an active region layer comprised of the AlGaN composition above is provided, as well as a method of producing the AlGaN composition and semiconductor UV light emitting device, involving molecular beam epitaxy.
1. A semiconductor-based ultraviolet light emitting device composition comprising:
a group III-Nitride containing AlGaN alloy having self-assembled nanometer-scale localized compositionally inhomogeneous regions wherein the localized compositionally inhomogeneous regions are nanometer in scale in more than one dimension,
wherein, when the alloy is optically or electrically injected or pumped, then luminescence occurs due to radiative recombination of carriers in the nanometer-scale inhomogeneous regions having band-gap energies less than surrounding material.
2. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy has a thickness of about 50 nanometers or greater.
3. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy contains an AlN mole fraction of between about 20 to 80%.
4. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy has a fine scale facetted surface morphology having pits with diameters of about 10 to 100 nanometers formed therein.
5. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy is doped with an impurity.
6. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy is doped with an impurity selected from the group consisting of silicon, magnesium, beryllium, germanium and carbon.
7. The semiconductor-based ultraviolet light emitting device composition of claim 1 having nanometer size localized compositionally inhomogeneous regions having band-gap energies less than surrounding material.
8. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy has a fine scale facetted surface morphology having pits with diameters of about 10 to 100 nanometers formed therein.
9. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN comprises a plurality of alternating layers of AlGaN alloy containing different AlN mole fractions and having nanometer size localized compositionally inhomogeneous regions therein.
10. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the active layer containing an AlGaN alloy is characterized by having regions in which the aluminum is not uniformly incorporated therein.
11. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the nanometer-scale localized compositionally inhomogeneous regions have a band-gap energy less than the surrounding material.
12. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy having nanometer-scale localized compositionally inhomogeneous regions is self-assembled.
13. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy having nanometer-scale localized compositionally inhomogeneous regions is self-assembled and comprises compositionally inhomogeneous regions characterized by having larger or smaller AlN mole fraction than the entire composition on average therein.
14. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein group III-Nitride active layer containing an AlGaN alloy having nanometer-scale localized, self-assembled compositionally inhomogeneous regions characterized by having larger or smaller AlN mole fraction than the entire composition on average therein, is made by a method comprising:
depositing an active layer containing an AlGaN alloy on a substrate or a film layer formed adjacent a substrate using plasma-assisted molecular beam epitaxy, wherein the deposition of the active layer containing an AlGaN alloy is conducted under the following conditions:
(a) deposition is performed under a facetted growth regime;
(b) the substrate temperature is maintained within a temperature range of from about 770 to 950° C.
(c) a nitrogen gas flow rate of from about 0.2 to 1.2 standard cubic centimeters per minute is maintained;
(d) the active layer containing an AlGaN alloy is grown at a rate of about 80 to 1000 nm/hour;
(e) the Al atom flux as measured by beam equivalent pressure is maintained at from about 1×10-8 to 2×10-7 Torr; and
(f) the Ga atom flux as measured by beam equivalent pressure is maintained at from about 2×10-7 to 2×10-6 Torr, producing an ultraviolet light emitting device having an active layer containing an AlGaN alloy having nanometer-scale localized, self-assembled compositionally inhomogeneous regions characterized by having larger or smaller AlN mole fraction than the entire composition on average therein.
15. The semiconductor-based ultraviolet light emitting device composition of claim 1 , further comprising a substrate having a top surface and wherein the self-assembled nanometer-scale localized compositionally inhomogeneous regions are disposed over the top surface of the substrate and are inhomogeneous in a direction having a vector projection parallel to the plane of the top surface of the substrate.
16. The semiconductor-based ultraviolet light emitting device composition of claim 1 , further comprising a substrate having a top surface and wherein the self-assembled nanometer-scale localized compositionally inhomogeneous regions are disposed over the top surface of the substrate and are inhomogeneous in a direction that is not perpendicular to the top surface of the substrate of the device.
17. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the self-assembled nanometer-scale localized compositionally inhomogeneous regions are not the result of separate layers.
18. The semiconductor-based ultraviolet light emitting device composition of claim 1 further comprising a substrate having a top surface and at least one layer between the substrate and the group III-Nitride containing AlGaN alloy having self-assembled nanometer-scale localized compositionally inhomogeneous regions disposed over the top surface of the layer.
19. The semiconductor-based ultraviolet light emitting device composition of claim 1 , wherein the group III-Nitride containing AlGaN alloy is doped with an impurity selected from the group consisting of silicon, magnesium, beryllium, germanium and carbon, and wherein the concentration of the impurity is from 10 14 to 10 20 atoms/centimeter 3 .
20. A semiconductor-based ultraviolet light emitting device composition comprising:
a group III-Nitride containing AlGaN alloy having nanometer-scale localized compositionally inhomogeneous regions,
wherein, when the alloy is optically or electrically injected or pumped, then luminescence occurs due to radiative recombination of carriers in the nanometer-scale size inhomogeneous regions having band-gap energies less than surrounding material
and further wherein the group III-Nitride containing AlGaN alloy is characterized by a fine scale, facetted surface morphology having surface pits on the order of about 10 to 100 nm wide.
21. The semiconductor-based ultraviolet light emitting device composition of claim 20 having nanometer size localized compositionally inhomogeneous regions having band-gap energies less than surrounding material.
22. The semiconductor-based ultraviolet light emitting device composition of claim 20 , wherein the active layer containing an AlGaN alloy is characterized by having regions in which the aluminum is not uniformly incorporated therein.
23. The semiconductor-based ultraviolet light emitting device composition of claim 20 , wherein the nanometer-scale localized compositionally inhomogeneous regions have a band-gap energy less than the surrounding material.
24. The semiconductor-based ultraviolet light emitting device composition of claim 20 , wherein the group III-Nitride containing AlGaN alloy having nanometer-scale localized compositionally inhomogeneous regions is self-assembled.
25. The semiconductor-based ultraviolet light emitting device composition of claim 20 , wherein the group III-Nitride containing AlGaN alloy having nanometer-scale localized compositionally inhomogeneous regions is self-assembled and comprises compositionally inhomogeneous regions characterized by having larger or smaller AlN mole fraction than the entire composition on average therein.