Semiconductor Structure and Method of Manufacturing a Semiconductor Structure

• US 20090127574A1
• Filed: 06/20/2006
• Published: 05/21/2009
• Est. Priority Date: 07/01/2005
• Status: Active Grant

• Current Assignee: Optogan Oy
• Original Assignee: Optogan Oy
• Inventors: Bougrov, Vladislav E., Odnoblyudov, Maxim A.
• Granted Patent: US 7,763,904 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A semiconductor structure is formed of nitrides of group III metals having wurtzite crystal structure and grown in vapor phase on a (0001) oriented semiconductor substrate. The structure comprises a bottom cladding layer, a top cladding layer, and a diffusion region positioned between the cladding layers for diffusing light propagating within the semiconductor structure. The diffuse region has refractive index different from those of the cladding layers and non-flat surfaces for providing light diffusing interfaces between the diffusion region and the cladding layers. According to the invention, the diffusion region comprises a plurality of diffusion layers, compositions and thicknesses of said diffusion layers having been chosen to avoid formation of strain-induced dislocations in the diffusion region, and adjacent diffusion layers having different refractive indices in order to further enhance the diffusion efficiency.

Claims

1. A semiconductor structure (1) formed of nitrides of group III metals having wurtzite crystal structure and grown in vapor phase on a (0001) oriented semiconductor substrate (2,3), the structure comprising:

a bottom cladding layer (4);

a top cladding layer (5) having a flat upper surface (9) grown above the bottom cladding layer, the lattice constant of the top cladding layer being the same as that of the bottom cladding layer; and

a diffusion region (6,7) positioned between the bottom cladding layer (4) and the top cladding layer (5) for diffusing light propagating within the semiconductor structure (1), the diffuse region having refractive index different from those of the cladding layers and non-flat surface for providing light diffusing interfaces between the diffusion region and the cladding layers,

characterized in that the diffusion region comprises a plurality of diffusion layers (6,7), compositions and thicknesses of said diffusion layers having been chosen to avoid formation of strain-induced dislocations in the diffusion region, and adjacent diffusion layers (6,7) having different refractive indices in order to further enhance the diffusion efficiency.

2. A semiconductor structure (1) according to claim 1, characterized in that said nitrides are of the form Al_xGa_1-x-yIn_yN, wherein 0≦

x≦

1 and 0≦

y≦

1.

3. A semiconductor structure (1) according to claim 1, characterized in that said bottom and top cladding layers are of the same material.

4. A semiconductor structure (1) according to claim 3, characterized in that the diffusion layers (6,7) are lattice to the cladding layers (4,5).

5. A semiconductor structure (1) according to claim 3, characterized in that the diffusion layers (6,7) are lattice mismatched to the bottom and the top cladding layers (4,5), thickness of each diffusion layer is smaller than the Matthews-Blakeslee critical thickness, and one of two adjacent diffusion layers have a positive and the other a negative lattice misfit to the cladding layers (4,5) in order to avoid strain accumulation in the diffusion layers.

6. A semiconductor structure (1) according to claim 1, characterized in that the bottom cladding layer and the diffusion layers have upper surfaces with facets having crystallographic indices other than (0001) and those of the type {1 100}.

7. A method of manufacturing a semiconductor structure (1) formed of nitrides of group III metals having wurtzite crystal structure and grown in vapor phase on a (0001) oriented semiconductor substrate (2,3), the method comprising steps of

growing in vapor phase a bottom cladding layer (4);

growing in vapor phase a diffusion region (6,7) above the bottom cladding layer for diffusing light propagating within the semiconductor structure (1), the diffusion region having a refractive index different from that of the bottom cladding layer and non-flat surfaces; and

growing in vapor phase a top cladding layer (5) above the diffusion region, the top cladding layer having a flat upper surface (9), a refractive index different from that of the diffusion region, and a lattice constant the same as that of the bottom cladding layer,

characterized in that the growing of the diffusion region comprises steps of growing a plurality of diffusion layers (6,7), compositions and thicknesses of the diffusion layers having been chosen to avoid formation of strain-induced dislocations in the layer interfaces, and adjacent diffusion layers (6,7) having different refractive indices in order to further enhance the diffusion efficiency.

8. A method according to claim 7, characterized in that said nitrides are of the form Al_xGa_1-x-yIn_yN, wherein 0≦

x≦

1 and 0≦

y≦

1.

9. A method according to claim 7, characterized in that said bottom and top cladding layers are of the same material.

10. A method according to claim 9, characterized in that diffusion layers (6,7) are grown having lattice constants the same as that of the cladding layers (4,5).

11. A method according to claim 9, characterized in that diffusion layers (6,7) are grown, each of them having a lattice constant different from that of the cladding layers (4,5), a thickness smaller than the Matthews-Blakeslee critical thickness, and one of two adjacent diffusion layers (6,7) having a lattice constant greater and the other a lattice constant smaller than that of the cladding layers (4,5) in order to avoid strain accumulation in the diffusion layers.

12. A method according to claim 7, characterized in that a bottom cladding layer and diffusion layers are grown, each of them having an upper surface with facets having crystallographic indices other than (0001) and those of the type {1 100}.

13. A method according to claim 12, characterized in that the growing of the bottom cladding layer comprises a step of formation of precipitates (14) on a (0001) oriented surface, said precipitates having a height of 0.1-1.5 μ

m and surface density of 10⁷-10⁸ cm<sup>−

2</sup>.

14. A method according to claim 13, characterized in that said precipitates (14) are formed by a process consisting of a sequence of short low-temperature depositions, performed in temperature range of 450-700°

C., followed by high-temperature layer annealing periods, performed in temperature range of 900-1150°

C.