Semiconductor light emitting device
A method for manufacturing a semiconductor light emitting device is provided. The device includes: an n-type semiconductor layer; a p-type semiconductor layer; and a light emitting unit provided between the n-type semiconductor layer and the p-type semiconductor layer. The method includes: forming a buffer layer made of a crystalline Al x Ga 1−x N (0.8≦x≦1) on a first substrate made of c-plane sapphire and forming a GaN layer on the buffer layer; stacking the n-type semiconductor layer, the light emitting unit, and the p-type semiconductor layer on the GaN layer; and separating the first substrate by irradiating the GaN layer with a laser having a wavelength shorter than a bandgap wavelength of GaN from the first substrate side through the first substrate and the buffer layer.
1. A semiconductor device comprising:
a first buffer layer made of a crystalline AlN and containing carbon;
a second buffer layer made of a crystalline Al x Ga 1−x N (0.8≦x≦1) provided on the first buffer layer and having a lower carbon concentration than the first buffer layer; and
a GaN layer provided on the second buffer layer,
wherein the first buffer layer is a layer having a carbon concentration of not less than 3×10 18 cm −3 and not more than 5×10 20 cm −3 , and a thickness of not less than 3 nanometers and not more than 20 nanometers, and
the second buffer layer is a layer having a carbon concentration of not less than 1×10 16 cm −3 and not more than 3×10 18 cm −3 , and a thickness of not less than 0.6 micrometers and not more than 6 micrometers.
2. The device according to claim 1 , wherein a total film thickness of the first buffer layer and the second buffer layer is 1 micrometer to 4 micrometers.
3. The device according to claim 1 , wherein the first buffer layer and the second buffer layer have a higher thermal conductivity than the GaN layer.
4. A semiconductor light emitting device comprising:
an n-type semiconductor layer;
a p-type semiconductor layer;
a light emitting unit provided between the n-type semiconductor layer and the p-type semiconductor layer;
a first buffer layer made of a crystalline AlN and containing carbon;
a second buffer layer made of a crystalline Al x Ga 1−x N provided on the first buffer layer and having a lower carbon concentration than the first buffer layer; and
a GaN layer provided on the second buffer layer,
wherein the p-type semiconductor layer includes a first p-type layer provided on the light emitting unit and a p-type contact layer provided on the first p-type layer,
the first p-type layer is Mg-doped p-type AlGaN formed to have a concentration profile including a higher Mg concentration on a side of the light emitting unit and a lower Mg concentration on a side opposite to the light emitting unit,
the first buffer layer is a layer having a carbon concentration of not less than 3×10 18 cm −3 and not more than 5×10 20 cm −3 , and a thickness of not less than 3 nanometers and not more than 20 nanometers, and
the second buffer layer is a layer having a carbon concentration of not less than 1×10 16 cm −3 and not more than 3×10 18 cm −3 , and a thickness of not less than 0.6 micrometers and not more than 6 micrometers.
5. The device according to claim 4 , wherein a total film thickness of the first buffer layer and the second buffer layer is 1 micrometer to 4 micrometers.
6. The device according to claim 4 , wherein the first buffer layer and the second buffer layer have a higher thermal conductivity than the GaN layer.
7. The device according to claim 4 , wherein the n-type semiconductor layer includes an Si-doped n-type GaN layer provided on the GaN layer, and an Si-doped n-type AlGaN layer provided on the Si-doped n-type GaN layer.
8. The device according to claim 7 , wherein the Si-doped n-type GaN layer has a silicon concentration of not less than 1×10 19 cm −3 and not more than 2×10 19 cm −3 , and the Si-doped n-type AlGaN layer has a silicon concentration lower than the silicon concentration of the Si-doped n-type GaN layer.
9. The device according to claim 4 , wherein the light emitting unit includes a multiple-quantum-well structure having barrier layers and well layers alternately stacked.
10. The device according to claim 9 , wherein the barrier layer is a Si-doped n-type AlGaInN and has a silicon concentration of 1.1×10 19 cm −3 to 3.0×10 19 cm −3 .
11. The device according to claim 4 , wherein the device further includes a spacer layer provided between the light emitting unit and the p-type semiconductor layer, and the spacer layer includes AlGaInN and has an Si concentration of 1×10 16 cm −3 to 3.0×10 18 cm −3 .
12. The device according to claim 4 , wherein a peak wavelength of emitted light of the light emitting unit is longer than 370 nanometers and shorter than 400 nanometers.
13. The device according to claim 4 , wherein at least one of projections or depressions is formed on a surface on a side of the p-type semiconductor layer opposite to the light emitting unit at a spacing not longer than a wavelength of emitted light of the light emitting unit.
14. The device according to claim 4 , wherein the light emitting unit includes a barrier layer made of an AlGaInN quarternary mixed crystal having an In component ratio in group III elements not less than 0.3% and not more than 2%.
15. The device according to claim 14 , wherein the AlGaInN quarternary mixed crystal has a Si concentration not less than 1.1×10 19 cm −3 and not more than 3.0×10 19 cm −3 .