Method of strain engineering and related optical device using a gallium and nitrogen containing active region
View Patent ↗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.
1. An optical device comprising:
a gallium and nitrogen containing substrate including a surface region and a first lattice constant;
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;
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;
an optical confinement region overlying the strain control region; and
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 device 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 device of claim 1 wherein the strained region functions as an optical confinement region.
4. The device 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 device 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 device 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 device of claim 1 further comprising:
at least one barrier region sandwiched between a pair of quantum well regions;
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 device 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 device of claim 1 wherein the strain control region comprises GaN, AlGaN, InAlGaN, or low indium content InGaN.
10. The device 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 device 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 device of claim 1 wherein the plurality of quantum wells are operable for an emission in a 510 to 550 nm range.
13. The device of claim 1 wherein the plurality of quantum wells are operable for an emission in a 430 to 480 nm range.
14. The device 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 device of claim 1 wherein the strain control region is configured to maintain a 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 device 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.
17. The method of claim 1 wherein:
the strained region causes the upper strain budget to be greater than the predetermined strain budget;
the predetermined strain budget maintains the plurality of quantum well regions free from defects; and
the step of determining the upper strain budget is for an entire growth structure including the plurality of quantum well regions.