Strain-controlled III-nitride light emitting device
View Patent ↗In a III-nitride light emitting device, a ternary or quaternary light emitting layer is configured to control the degree of phase separation. In some embodiments, the difference between the InN composition at any point in the light emitting layer and the average InN composition in the light emitting layer is less than 20%. In some embodiments, control of phase separation is accomplished by controlling the ratio of the lattice constant in a relaxed, free standing layer having the same composition as the light emitting layer to the lattice constant in a base region. For example, the ratio may be between about 1 and about 1.01.
1. A semiconductor light emitting device comprising:
a nucleation region; and
an epitaxial structure comprising:
a base region formed on the nucleation region; and
a III-nitride light emitting layer overlying the base region and disposed between an n-type region and a p-type region and overlying the base region; wherein:
the light emitting layer is configured to emit light having a peak emission wavelength greater than 420 nm; and
the light emitting layer and base region are configured such that:
the light emitting layer has an average InN composition b; and
an InN composition at any point in the light emitting layer is between (b−0.2b) and (b+0.2b).
2. The device of claim 1 wherein the InN composition at any point in the light emitting layer is between (b−0.1b) and (b+0.1b).
3. The device of claim 1 wherein InN composition at any point in the light emitting layer is between (b−0.05b) and (b+0.05b).
4. The device of claim 1 wherein the light emitting layer is InGaN.
5. The device of claim 1 wherein the base region is Al x In y Ga z N, where 0≦x≦1, 0≦y≦1, and 0≦z≦1.
6. The device of claim 1 wherein the base region is In x Ga y N, where 0≦x≦1 and 0≦y≦1.
7. The device of claim 1 wherein a dislocation density in the n-type region, light emitting layer, and p-type region is less than about 5×10 8 cm −2 .
8. The device of claim 1 wherein the light emitting layer and any layers between the light emitting layer and the base region are strained.
9. A semiconductor light emitting device comprising:
a nucleation region; and
an epitaxial structure comprising:
a base region formed on the nucleation region; and
a III-nitride light emitting layer overlying the base region and disposed between an n-type region and a p-type region; wherein the light emitting layer and base region are configured such that:
the light emitting layer has an average InN composition b;
the average InN composition b is greater than 8%; and
an InN composition at any point in the light emitting layer is between (b−0.2b) and (b+0.2b).
10. The device of claim 9 wherein the InN composition at any point in the light emitting layer is between (b−0.1b) and (b+0.1b).
11. The device of claim 9 wherein InN composition at any point in the light emitting layer is between (b−0.05b) and (b+0.05b).
12. The device of claim 9 wherein the light emitting layer is AlInGaN.
13. The device of claim 9 wherein:
the base region has a lattice constant a 1 ;
a relaxed, free standing layer having a same composition as the light emitting layer has a lattice constant a 2 ; and
a ratio of a 2 to a 1 is between about 1 and about 1.01.
14. The device of claim 9 wherein the base region is Al x In y Ga z N, where 0≦x≦1,0≦y≦1, and 0≦z≦1.
15. The device of claim 9 wherein the light emitting layer is configured to emit light having a peak emission wavelength greater than 420 nm.