LED device and method of manufacture

1 . A method of manufacturing an LED device, comprising the steps of:

forming an n-doped connecting layer of III-nitride material over a porous region of III-nitride material;

forming a first electrically-insulating mask layer on the n-doped connecting layer;

removing a portion of the first mask layer to expose a first exposed region of the n-doped connecting layer;

forming a first LED structure, which is configured to emit light at a first emission wavelength, on the first exposed region of the n-doped connecting layer;

forming a second electrically-insulating mask layer over the first LED structure and the n-doped connecting layer;

removing a portion of the second mask layer to expose a second exposed region of the n-doped connecting layer; and

forming a second LED structure, which is configured to emit light at a second emission wavelength different from the first emission wavelength, on the second exposed region of the n-doped connecting layer,

in which the n-doped connecting layer of III-nitride material is formed over the porous region of III-nitride material and a non-porous region of III-nitride material, the porous region being disposed in a plane of the LED device and the non-porous region being disposed in the same plane.

2 . A method according to claim 1 , in which one of the first LED structure and the second LED structure is positioned over the porous region, and the other is positioned over the non-porous region, or in which both the first LED structure and the second LED structure are positioned over the porous region.

3 . A method according to claim 1 , comprising the step of forming the porous region of III-nitride material by electrochemical porosification through a non-porous layer of III-nitride material, such that the non-porous layer of III-nitride material forms a non-porous intermediate layer over the porous region prior to forming the n-doped connecting layer, and optionally comprising the step of etching the non-porous intermediate layer to reduce its thickness, prior to forming the n-doped connecting layer of III-nitride material over the non-porous intermediate layer.

4 . A method according to claim 1 , in which the porous region of III-nitride material comprises a stack of multiple porous layers of III-nitride material; in which the stack of porous layers is a stack of alternating porous and non-porous layers.

5 . A method according to claim 1 , in which the porous region has a porosity of between 10% and 90% porous and/or in which the n-doped connecting layer of III-nitride material has a thickness of between 100 nm and 2000 nm and a charge carrier concentration of >1×10 17 cm −3 .

6 . A method according to claim 1 , in which the first mask layer is formed from one of: SiO 2 , SiN, SiON, and/or the second mask layer is formed from one of: SiO 2 , SiN, SiON, aluminium oxide, tantalum oxide, hafnium oxide, or a combination thereof and/or in which the first electrically-insulating mask layer or the second electrically-insulating mask layer has a thickness of between 20 nm and 1000 nm.

7 . A method according to claim 1 , in which the first exposed region and/or the second exposed region of the connecting layer are circular, square, rectangular, hexagonal, or triangular in shape and/or in which the first exposed region and/or the second exposed region have a width of between 0.05 μm and 100 μm.

8 . A method according to claim 1 , comprising the step of, after the second LED structure has been formed, removing a portion of the second electrically-insulating mask layer to expose a region of the first LED structure; and

forming an electrical contact in the exposed region of the first LED structure.

9 . A method according to claim 1 , comprising the step of exposing a portion of the n-doped connecting layer, and forming an electrical contact in the exposed portion of the n-doped connecting layer.

10 . A method of manufacturing a three colour LED device, comprising the steps of:

forming an n-doped connecting layer of III-nitride material over a porous region of III-nitride material and a non-porous region of III-nitride material;

forming a first electrically-insulating mask layer on the n-doped connecting layer;

removing a portion of the first mask layer to expose a first exposed region of the n-doped connecting layer over the porous region,

removing a portion of the first mask layer to expose a second exposed region of the n-doped connecting layer over the non-porous region;

forming a first LED structure, which is configured to emit light at a first emission wavelength, on the first exposed region of the n-doped connecting layer;

forming a second LED structure, which is configured to emit light at a second emission wavelength, on the second exposed region of the n-doped connecting layer;

forming a second electrically-insulating mask layer over the first LED structure, the second LED structure, and the n-doped connecting layer;

removing a portion of the second mask layer to expose a third exposed region of the n-doped connecting layer; and

forming a third LED structure, which is configured to emit light at a third emission wavelength different from the first emission wavelength and the second emission wavelength, on the third exposed region of the n-doped connecting layer.

11 . A method according to claim 10 , in which the second LED structure is identical to the first LED structure, and in which the first LED structure and the second LED structure are formed simultaneously, and/or in which the third exposed region of the n-doped connecting layer is formed above the non-porous region of III-nitride material.

12 . An LED device, comprising:

an n-doped connecting layer of III-nitride material over a porous region of III-nitride material;

an electrically-insulating mask layer on the n-doped connecting layer;

a first LED structure, configured to emit light at a first emission wavelength, and

a second LED structure, configured to emit light at a second emission wavelength different from the first emission wavelength,

in which a portion of the first and second LED structures extend through a gap in the electrically-insulating mask layer, and are in contact with the n-doped connecting layer,

in which the n-doped connecting layer of III-nitride material extends over the porous region of III-nitride material and a non-porous region of III-nitride material, the porous region being disposed in a plane of the LED device and the non-porous region being disposed in the same plane.

13 . An LED device according to claim 12 , in which one of the first LED structure and the second LED structure is positioned over the porous region and the other is positioned over the non-porous region, or in which both the first LED structure and the second LED structure are positioned over the porous region.

14 . An LED device according to claim 12 , in which the first LED structure comprises:

a first n-doped portion;

a first p-doped portion; and

a first light emitting region located between the first n-doped portion and the first p-doped portion,

and the second LED structure comprises:

a second n-doped portion;

a second p-doped portion; and

a second light emitting region located between the second n-doped portion and the second p-doped portion.

15 . An LED device according to claim 14 , in which the first light-emitting region and/or the second light-emitting region comprises one or more III-nitride light-emitting layers, and in which the or each light-emitting layer comprises a quantum well, or a nanostructured layer comprising quantum dots, or fragmented or discontinuous quantum wells.

16 . An LED device according to claim 15 , in which the one or more light-emitting layers in the first LED structure have a composition In x Ga 1-x N, in which 0.10≤x≤0.40, or 0.18≤x≤0.30, or 0.22≤x≤0.30, and/or in which the one or more light-emitting layers in the second LED structure have a composition In y Ga 1-y N, in which 0.20≤y≤0.40, or 0.26≤y≤0.40, or 0.30≤y≤0.40.

17 . A three colour LED device, comprising:

an n-doped connecting layer of III-nitride material over a porous region of III-nitride material;

an electrically-insulating mask layer on the n-doped connecting layer;

a first LED structure, configured to emit light at a first emission wavelength,

a second LED structure, configured to emit light at a second emission wavelength different from the first emission wavelength, and

a third LED structure, configured to emit light at a third emission wavelength different from the first and second emission wavelengths,

in which a portion of the first, second and third LED structures are in contact with the n-doped connecting layer, and in which the first LED structure is positioned over the porous region of III-nitride material, and the second LED structure is not positioned over the porous region of III-nitride material.

18 . A three colour LED device according to claim 17 , in which one or more light-emitting layers in the first LED structure and the second LED structure have the composition In x Ga 1-x N, in which 0.10≤x≤0.40, or 0.18≤x≤0.30, or 0.22≤x≤0.30.

19 . A three colour LED device according to claim 18 , in which the second LED structure is identical to the first LED structure, and in which the first LED structure and the second LED structure emit light at different emission wavelengths due to the porous region beneath the first LED structure.

20 . A three colour LED device according to claim 17 , in which the third LED structure is not positioned over the porous region of III-nitride material, and/or in which the third LED structure is configured to emit light at a peak wavelength between 400 and 500 nm under electrical bias thereacross.

21 . A three colour LED device according to claim 17 , in which one or more light-emitting layers in the third LED structure have a composition In z Ga 1-z N, in which 0.10≤z≤0.30, or 0.12≤z≤0.25, or 0.15≤z≤0.20.

22 . A three colour LED device according to claim 17 , in which the first, second and third LED structures are configured so that:

the first LED structure emits light at a peak wavelength between 600 and 650 nm under electrical bias thereacross;

the second LED structure emits light at a peak wavelength between 515 and 550 nm under electrical bias thereacross; and

the third LED structure emits light at a peak wavelength between 415 and 500 nm under electrical bias thereacross.