Method of strain engineering and related optical device using a gallium and nitrogen containing active region

• US 9,379,522 B1
• Filed: 07/28/2014
• Issued: 06/28/2016
• Est. Priority Date: 11/05/2010
• Status: Active Grant

• Current Assignee: Kyocera SLD Laser Incorporated (Kyocera Corporation)
• Original Assignee: Soraa Laser Diode, Inc. (Kyocera Corporation)
• Inventors: Raring, James W., Elsass, Christiane Poblenz
• Primary Examiner(s): Menz, Laura
• Application Number:
  US14/444,687
• Time in Patent Office: 701 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/02389 Nitrides
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/12 with a stress relaxation structure, e.g. buffer layer
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01S 5/1082 with a special facet structure, e.g. structured, non planar, oblique
• CPC Class Codes: H01S 5/2009 by using electron barrier layers
• CPC Class Codes: H01S 5/2018 Optical confinement, e.g. absorbing-, reflecting- or waveguide-layers
• CPC Class Codes: H01S 5/2031 characterized by special waveguide layers, e.g. asymmetric waveguide layers or defined bandgap discontinuities
• CPC Class Codes: H01S 5/2201 in a specific crystallographic orientation
• CPC Class Codes: H01S 5/3063 using Mg
• CPC Class Codes: H01S 5/3201 incorporating bulkstrain effects, e.g. strain compensation, strain related to polarisation
• CPC Class Codes: H01S 5/3202 grown on specifically orientated substrates, or using orientation dependent growth
• CPC Class Codes: H01S 5/320275 semi-polar orientation
• CPC Class Codes: H01S 5/3213 : asymmetric clading layers
• CPC Class Codes: H01S 5/3403 : having a strained layer structure in which the strain performs a special function, e.g. general strain effects, strain versus polarisation
• CPC Class Codes: H01S 5/3406 : including strain compensation
• CPC Class Codes: H01S 5/34333 : with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
• CPC Class Codes: H01S 5/34346 : characterised by the materials of the barrier layers

Abstract

An optical device has a gallium and nitrogen containing substrate including a surface region and a strain control region, the strain control region being configured to maintain a quantum well region within a predetermined strain state. The device also has a plurality of quantum well regions overlying the strain control region.

Claims

1. A method for fabricating an optical device comprising:

providing a gallium and nitrogen containing substrate including a surface region and a first lattice constant;

forming a strained region overlying the surface region, the strained region having a second lattice constant, the second lattice constant being larger than the first lattice constant;

forming a strain control region having a third lattice constant, the third lattice constant being substantially equivalent to the second lattice constant, the strain control region being configured to maintain at least a quantum well region within a predetermined strain state;

forming an optical confinement region overlying the strain control region; and

forming a plurality of quantum well regions overlying the optical confinement region, each of the plurality of quantum well regions having a fourth lattice constant, the fourth lattice constant being substantially equivalent to the second lattice constant, whereupon the strain control region has a higher bandgap than the strained region and the quantum well regions.

2. The method of claim 1 wherein:

the strained region is highly strained and functions as an optical confinement layer;

the optical device comprises one of a light emitting diode and a laser device;

the strained region comprises an interface region between the substrate and the stain control region; and

the interface region comprises a plurality of dislocations configured within at least one location of the interface region to relieve strain within the strained region.

3. The method of claim 1 wherein the strained region functions as an optical confinement region.

4. The method of claim 1 wherein:

the surface region is configured in a non-polar orientation or a {20-21} semi-polar orientation;

each of the first lattice constant, the second lattice constant, and the third lattice constant are parallel to a projection of a c-direction;

the first lattice constant and the second lattice constant are characterized by first tilt angle and a second tilt angle different from each other by more than 0.5 degrees.

5. The method of claim 1 wherein the surface region is configured to be in an off-set of a {20-21} orientation and wherein the strained region is at least partially relaxed.

6. The method of claim 1 wherein the plurality of quantum well regions comprises 3 to 7 quantum wells, each of the quantum wells comprising substantially InGaN;

and wherein the plurality of quantum well regions range in thickness from 2 nm to 8 nm.

7. The method of claim 1 further comprising:

forming at least one barrier region sandwiched between a pair of quantum well regions;

whereupon each of the barrier regions comprising GaN, InGaN, AlGaN, or AlInGaN; and

each of the barrier regions ranges in thickness from 1.5 nm to 12 nm.

8. The method of claim 1 wherein:

the strained region comprises a low Al content InAlGaN;

the strained region has a thickness ranging from about 40 to about 80 nm with about 12 to about 16% indium content;

the strained region has a thickness ranging from about 70 to about 500 nm with about 8 to about 25% indium content; and

the strained region is doped with an n-type species of at least one of Si or Mg.

9. The method of claim 1 wherein the strain control region comprises GaN, AlGaN, InAlGaN, or low indium content InGaN.

10. The method of claim 1 wherein the strain control region maintains a strain budget within a predetermined range selected to maintain the plurality of quantum wells substantially free from a defect threshold.

11. The method of claim 1 wherein the optical confinement region between the strain control region and the plurality of quantum wells is an SCH region comprised of InGaN or low Al content InAlGaN with a thickness ranging from 10 nm to 100 nm and an indium content ranging from 1% to about 10%.

12. The method of claim 1 wherein the plurality of quantum wells are operable for an emission in a 510 to 550 nm range.

13. The method of claim 1 wherein the plurality of quantum wells are operable for an emission in a 430 to 480 nm range.

14. The method of claim 1 further comprising a strain budget of Q characterizing a cumulative strain characteristic associated with an entire growth structure including at least the plurality of quantum well regions and a contribution from the strain control region;

whereupon the strain budget Q is greater than a total strain associated with the entire growth structure excluding the contribution from the strain control region.

15. The method of claim 1 wherein the strain control region is configured to maintain an entire growth structure including the plurality of quantum well regions below a defect threshold, the defect threshold being an upper level of defects within the plurality of quantum well regions tolerable to maintain a desired photoluminescence level and a desired electroluminescence level, the defect threshold being above the upper level of defects within the plurality of quantum well regions without the strain control region.

16. The method of claim 1 wherein:

the strained region comprises a gallium and nitrogen containing material with InGaN overlying the surface region of the substrate;

the plurality of quantum well regions emit electromagnetic radiation characterized by an optical mode spatially disposed at least partially within the quantum well region; and

the gallium and nitrogen containing material is configured with a thickness and an indium content to manipulate a confinement of the optical mode and configured to absorb a stray and/or leakage of the emission of electromagnetic radiation.